The European Union is to set up a joint working group with Turkey to stop the build up of migrants at the country's border with Greece.

But EU officals warned Turkish President Recep Tayyip Erdogan not to trigger a renewed migrant crisis, during discussions between the two sides in Brussels.

The talks involved Mr Erdogan, European Council President Charles Michel, European Commission President Ursula von der Leyen, and also NATO Secretary-General Jens Stoltenberg.

European leaders are considering taking in 1,500 child refugees to ease pressure on overwhelmed camps on Greek islands facing a new wave of arrivals from Turkey.

But Ms von der Leyen said there was no immediate concrete offer of new funding to revive a deal with Turkey to keep refugees from Syria and beyond.

"We will restart the dialogue," she said, ahead of her meeting with Mr Erdogan, adding that there would be "considerable discussions in the next few days and weeks."

Pressed on whether more money was on the table to appease Turkey's concerns, she said: "I was already very clear that we are at the beginning, and no numbers are being discussed at the very start."

Tens of thousands of asylum-seekers have been trying to break through the land border from Turkey for a week after Ankara announced it would no longer prevent people from trying to cross into the EU.

Turkey, which hosts around four million mostly Syrian refugees, has repeatedly railed against what it describes as unfair burden-sharing.

Mr Erdogan called on Greece to "open the gates" to the migrants after Greek police used tear gas and water cannon in skirmishes with crowds at the border.

"I hope I will return from Belgium with different outcomes," he said in a speech in Istanbul yesterday as he announced the meeting.

"Hey Greece! I appeal to you ... open the gates as well and be free of this burden," he said, adding: "Let them go to other European countries."

Today, Mr Erdogan's communications director Fahrettin Altun repeated allegations - denied by Greece - that border authorities have used excessive force against migrants.

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"The refugee crisis isn't going away," he tweeted. "The European Union cannot just throw money at this problem or solve it with excessive and lethal force ... It's time take meaningful steps together."

Early today, Germany said the EU was considering taking in up to 1,500 migrant children who are currently housed in Greek camps.

Ms von der Leyen said France, Portugal, Luxembourg and Finland had also offered to take in some.

In Berlin, German Chancellor Angela Merkel's spokesman said Turkey "bears a clear responsibility" for sending the refugees to the border and that it was trying to put its own problems "onto the backs on these people."

On Friday, Mr Erdogan ordered the Turkish coastguard to prevent risky Aegean sea crossings after more than 1,700 migrants landed on Lesbos and four other Aegean islands.

But Turkey's policy of allowing migrants and refugees to leave by land remains in place, and the instruction only affects sea crossings.

In 2016, Turkey and the EU agreed a deal whereby Brussels would provide billions of euros in aid in exchange for Turkish authorities curbing the flow of migrants.

But Ankara has repeatedly accused the bloc of not fulfilling promises that were made while Europe suffered its worst refugee crisis since the Second World War. Over a million people fled to the continent in 2015.

EU foreign policy chief Josep Borrell and Mr Michel met Mr Erdogan in Ankara on Wednesday as Turkey demanded greater support over the conflict and migrants.

After the talks, Mr Borrell promised an additional €170m in aid for vulnerable groups in Syria.

Mr Erdogan has felt extra pressure as nearly one million people in Syria's northwestern province of Idlib fled towards the Turkish border during the recent Syrian regime assault backed by Russia and Iran.

But the president and his Russian counterpart Vladimir Putin agreed a ceasefire on Thursday after Turkey launched an offensive against Damascus following the deaths of 59 Turkish security personnel in attacks blamed on the regime.