French President Emmanuel Macron has said that the United States faces a "credibility test" over its response to Russia dragging its feet on a Ukraine ceasefire.
Russia has rebuffed calls for an immediate ceasefire and kept up an intense bombardment of Ukraine even as diplomatic efforts to end the war have gained momentum.
US President Donald Trump called Vladimir Putin "crazy" late on Sunday in a rare rebuke of the Russian leader but he has yet to follow up on repeated threats to impose fresh sanctions on Russia.
President Macron said that if Russia gives "confirmation that it is not ready to make peace" the US must then confirm its "commitment" to impose sanctions on Russia, stressing it was a "credibility test for the Americans".
"I spoke 48 hours ago to President Trump who showed his impatience. The question now is what do we do? We (Europeans) are ready," he said during a visit to Singapore.
Mr Macron will give the opening speech at the Shangri-La Dialogue in Singapore, Asia's main annual security and defence conference, which was addressed last year by Ukrainian President Volodymyr Zelensky.
The French leader said this week he believed President Trump now realised Mr Putin lied when he claimed to be ready for peace in Ukraine, and hoped the US president's anger would translate into action.
Mr Macron said it was time to threaten Russia with "much more massive sanctions" to persuade it to end the conflict begun by its invasion of Ukraine in 2022.
The French president visited Kyiv on 10 May with other European leaders to give Russia an ultimatum, agreed with the US, to accept a ceasefire.
The Russian offensive has resulted in tens of thousands of deaths and the destruction of large parts of eastern and southern Ukraine.
Russian concern over NATO enlargement is fair - US envoy
US President Donald Trump's envoy to Ukraine Keith Kellogg said Russia's concern over the eastward enlargement of NATO is fair and the United States did not want to see Ukraine in the US-led military alliance.
Asked by US network ABC News about a Reuters report that Russia wanted a written pledge over NATO not enlarging eastwards to include Ukraine and other former Soviet republics, Mr Kellogg said: "It's a fair concern."
"We've said that to us, Ukraine coming into NATO is not on the table, and we're not the only country that says that - you know I could probably give you four other countries in NATO and it takes 32 of the 32 to allow you to come in to NATO," he told ABC last night.
"That's one of the issues that Russia will bring up," he added.
"They're not just talking Ukraine, they're talking the country of Georgia, they're talking Moldova," Mr Kellogg said, adding that a decision on US views of NATO enlargement was for President Trump to make.
Mr Kellogg said the sequencing of the peace talks would include an attempt to merge the two memorandums drafted by Ukraine and Russia into one single document with talks in Turkey on Monday.
"When we get into Istanbul next week we'll sit down and talk," Mr Kellogg said, adding that the national security advisers from Germany, France and Britain would join discussions on the memorandum with the United States.
Mr Kellogg said President Trump was "frustrated" with Russia because he had seen "a level of unreasonableness" from Russian President Vladimir Putin.
He scolded Russia for striking Ukrainian cities and said he had told Ukraine to turn up to talks.
A conservative estimate of dead and injured in the Ukraine war - from both sides combined - totals 1.2 million, he said.
"That is a stunning number - this is war on an industrial scale," Mr Kellogg said.
Meanwhile, Russian forces launched a massive drone attack overnight that injured several people, including two teenagers, in Ukraine's northeastern Kharkiv region, local officials said..
Eight people, including two 16-year-olds, were injured in an attack in the village of Vasyliv Khutir, Governor Oleh Syniehubov said.
He gave no further details.
The Ukrainian Air Force said that Russia launched 90 drones and two ballistic missiles overnight against Ukraine that targeted the Kharkiv, Odesa and Donetsk regions.
The Kharkiv region's main city also came under Russian drone attack which targeted a trolleybus depot and injured two people, Mayor Ihor Terekhov said.
"Today, Kharkiv suffered another attack: the enemy fired 8 'shaheds' at one of the depots where our trolleybuses were being repaired and maintained," he said on the Telegram messaging app.
He added that more than 30 nearby apartment buildings were damaged, while one trolleybus was completely destroyed, and 18 others sustained varying degrees of damage.
Kharkiv, Ukraine's second-largest city situated some 30km from the country's northeastern border, has been a repeated target of Russian air attacks.
Reuters could not independently verify the reports. There was no immediate comment from Russia.
Both sides deny targeting civilians in the war that Russia started with its full-scale invasion of Ukraine more than three years ago.
