European Union leaders have held talks with United Nations chief Antonio Guterres on global food security and sanctions imposed on Russia over its invasion of Ukraine.
They have also endorsed a plan to supply more artillery shells to Kyiv.
Mr Guterres' participation in the EU summit came days after the renewal of a deal brokered by the UN and Turkey on the safe export of Ukrainian grain via the Black Sea that is seen as crucial to overcoming a global food crisis.
German Chancellor Olaf Scholz said the bloc wanted "to ensure that Russia's horrible war of aggression against Ukraine would not result in food insecurity in the world".
"We need to ensure that grain exports, for example from Ukraine, can continue," he said.
Estonian Prime Minister Kaja Kallas spoke against any easing of sanctions on Moscow under the grain deal and called for a tighter price cap on Russian oil exports.
Joining by video, Ukrainian President Volodymyr Zelensky implored Europe to speed up and increase the supply of weapons - including long-range missiles and modern aircraft - and impose additional sanctions on Russia, or risk the war dragging on.
"If Europe hesitates, the evil may have time to regroup and prepare itself for years of war," he said in a video address recorded on a train that he said was en route to Ukraine's southern region of Kherson, recaptured by Kyiv last year.
EU chief executive, Commission President Ursula von der Leyen, said any new sanctions against Russia would mostly crackdown on circumvention.
She also said the EU would work with other organisations to find Ukrainian children deported to Russia and press for their return.
The International Criminal Court issued an arrest warrant for Russian President Vladimir Putin last week for illegal deportation of Ukrainian children.
"It is a horrible reminder of the darkest times of our history... to deport children. This is a war crime," she said.
"We know today of 16,200 children that have been deported. Only 300 have returned."
Mr Guterres did not speak to reporters after his talks with the EU leaders. The UN said in a statement that he had "provided an update on enhancing global food security through the Black Sea Grain Initiative and efforts to facilitate the exports of Russian food and fertilisers."
The US has pushed back against Russian demands that Western sanctions be eased before Moscow allows Ukrainian Black Sea grain exports to continue beyond mid-May, saying there are no restrictions on Russian farm products or fertilisers.
Inside the EU, the issue of fertiliser exports is blocking more sanctions against Russia's ally, Belarus. The bloc says new sanctions are needed to stop Belarus from serving as a route to bypass the existing Russia trade restrictions.
But Lithuania opposes what it calls "fertiliser oligarch" exemptions proposed to ensure Belarusian fertilisers continue flowing to third countries, arguing that that would weaken the sanctions regime overall, diplomats said.
Proponents say such carve-outs, similar to those the EU has in place under its sanctions against Russia, are necessary to ensure food security and refute Moscow's charge that EU measures- rather than Russia's invasion - are driving the global crisis.
There was no sign of any breakthrough on the issue at the summit.
AMMUNITION PLAN
The EU leaders endorsed a plan - agreed by foreign ministerson Monday - to send a million artillery shells to Ukraine overthe next year.
Officials say Ukraine is burning through shells at a fasterrate than its allies can produce them, prompting a renewedsearch for ammunition and ways to boost production, whichrequires more money as the war enters its 14th month.
The EU earmarked €1 billion for the swift supply of shells - and possibly missiles - from existing stocks and another €1 billion for joint orders by EU countries for more rounds.
The money will come from the European Peace Facility, an EU fund that has already earmarked several billion euros for military aid to Ukraine.
Today, the summit began discussions on topping it up with another 3.5 billion euros.
"We need to support Ukraine to defend itself, we need to continue to show solidarity and avoid any sign of fatigue," European Parliament head Roberta Metsola said after joining the leaders for part of the summit.
Officials say Ukraine is burning through shells at a faster rate than its allies can produce them, prompting a renewed search for ammunition and ways to boost production, which requires more money as the war enters its 14th month.
The EU earmarked €1bn for the swift supply of shells - and possibly missiles - from existing stocks and another €1bn for joint orders by EU countries for more rounds.
The money will come from the European Peace Facility, an EU fund that has already earmarked several billion euros for military aid to Ukraine. Today, the summit began discussions on topping it up with another €3.5bn.
Windsor Framework
Taoiseach Leo Varadkar is also in Brussels for the meeting of European Union leaders where the Windsor Framework will be discussed.
The meeting comes after EU member states approved the framework on Tuesday, and a key element of it - the Stormont brake - was endorsed by the House of Commons yesterday.
Mr Varadkar said it was premature to talk about direct rule by Westminster if Stormont is not restored, but that it was "the consistent position of the Irish Government that direct rule is not provided for in the Good Friday Agreement, and we couldn't support going back to that."
The Taoiseach welcomed yesterday’s vote on the Stormont Brake as very positive.
"I'm confident that the UK government and the European Union will implement the Windsor Framework now in good faith. And that's going to be to the benefit of people in Northern Ireland in particular," he said.
The Democratic Unionist Party voted against the brake, with leader Jeffrey Donaldson saying it wanted assurances that EU law could not impede Northern Ireland's ability to trade with the rest of the UK.
Speaking ahead of the European Council meeting, Mr Varadkar said he was joining other EU leaders in Brussels "to reaffirm our solidarity and continued political, economic, military, financial and humanitarian support to Ukraine".
"As we have said before, we will stand with Ukraine for as long as it takes.
"We will discuss recent developments regarding the Windsor Framework and there will be an important discussion on economic issues, including how to ensure Europe's future prosperity.
"I will be encouraging further work to improve the competitiveness of the European economy, making the most out of our single market, to drive future growth.
"We need to accelerate the green transition, boost skills, strengthen the single market and maintain an open and ambitious trade policy."
Šefčovič to visit London
European Commission Vice-President Maroš Šefčovič is due to travel to London tomorrow, where he is to meet with Foreign Secretary James Cleverly and Mr Heaton-Harris as part of the EU-UK Joint Committee.
This was a body set up as part of the Brexit process to oversee the implementation of the protocol and facilitate any changes as may have been required.
The topics officially on the summit agenda are support for Ukraine, notably the coordinated procurement of ammunition, as well as EU competitiveness and proposals for a revamp of energy market rules, the official said.
The EU should show it stood for free and fair trade by continuing to conclude free trade agreements with other regions such as South America's Mercosur and countries like Kenya, Australia, India and Indonesia, they said.
"We are in competition with China here, so it is in our interest to remain ahead and push for a rules-based, fair approach," the official added.
EU ban on fossil fuels cars not on summit agenda - German official
The EU's planned ban on new combustion engines from 2035 is not on the agenda of the summit but talks between the European Commission and Germany about their differences over the issue are "very constructive", a German government official said.
"We are confident that we will soon come to a solution," the official added. "The discussions are very, very constructive."
After months of negotiations, the European Parliament, the European Commission and member states agreed last year that new cars sold in the EU from 2035 to have zero CO2 emissions - effectively making it impossible to sell combustion engine cars from that date.
But Germany this month declared its last-minute opposition in an unusual move that sparked indignation among some EU diplomats.
It wants sales of new cars with internal combustion engines to be allowed after that date if they run on e-fuels.
The official reiterated Germany's position that this was part of the EU's original agreement - "that is sometimes forgotten".
"There is nothing negative about the fact we are insisting on this," the official said. "This is completely normal European procedure".
Additional reporting Tony Connelly, Reuters and PA
