Image source, Reuters

European Commission President Jean-Claude Juncker has confirmed that EU leaders could have to gather again.

"In the event the withdrawal agreement will not be approved by the House [of Commons] we have to come back," he says.

Image source, UK Parliament

A petition calling on Theresa May to cancel Brexit by revoking Article 50 has attracted more than 980,000 signatures.

Parliament's petitions website crashed earlier because of the high volume of traffic. It is now back up and running.

Foreign Secretary Jeremy Hunt told BBC Radio 4's Today that revoking Article 50 was possible but "highly unlikely".

Commons leader Andrea Leadsom said she had been made aware of technical problems with the site, but she dismissed the petition as not being on the same scale as the pro-Brexit vote in the 2016 referendum.

"Should it reach 17.4 million respondents then I am sure there will be a very clear case for taking action," she told MPs.

Image source, Getty Images

Speaking at the summit, German Chancellor Angela Merkel says: "We all must be aware that we are dealing with something of historical importance and therefore, we must also tread carefully and above all do everything possible to the last hour to ensure that there may be an orderly exit for the United Kingdom from the European Union."

BBC News Channel

BBC political correspondent Vicki Young says "no one really knows what is going on and how it's going to work next week".

She questions whether - if Theresa May’s deal is rejected again - Parliament can force her to go back to the EU and ask for a long Brexit delay.

This is something Theresa May has said she will not do, Vicki Young adds.

There is a lot of pressure on the prime minister, she says.

Image source, Reuters

French President Emmanuel Macron says: "Prime Minister Theresa May has asked - in the case of a positive vote in the British Parliament - for a purely technical extension.

"I am quite open to a technical extension. It should be as short as possible - in the case of a positive vote.

"The exit process has taken two years of negotiation. It cannot be renegotiated."

Mr Macron says it is necessary to be "clear" about the consequences of Mrs May losing a third Commons vote on her deal: "In the case of a negative vote in the British Parliament, we will be going to a no-deal, we all know that.

"It is absolutely essential to be clear in these days and these moments, because it is a matter of the good functioning of the EU.

"We cannot have what I would call an excessive extension which would harm our capacity to decision and to act," he adds.

Image source, AFP/ Getty Images

Arriving at the summit, French President Emmanuel Macron says: "In the case of a negative British vote [against Theresa May's deal], then we'd be heading to a no deal."

And speaking earlier in the week, German Chancellor Angela Merkel said the EU could agree to Mrs May's request to delay Brexit if in the next week there was a "positive vote" on the withdrawal agreement in the UK Parliament.

Taoiseach (Irish PM) Leo Varadkar says the situation in London is "somewhat chaotic", adding that "we need to cut the entire British establishment a little bit of slack on this".

European Commission president Jean-Claude Juncker has said: "If Great Britain does not leave at the end of March, then we are, I am sorry to say, in the hands of God. And I think even God sometimes reaches a limit to his patience."

BBC News Channel

BBC political correspondent Chris Morris says this is the EU 27's first formal discussion on extending Article 50 - by which the UK will leave the European Union.

He says the statement put forward by the president of the EU Commission Jean-Claude Juncker that an extension past the 22 May would be "difficult" is also "favoured by many others".

"A short extension of Brexit is not guaranteed."

Chris Morris also says that in the UK Parliament, the numbers do not look good for the prime minister's withdrawal agreement being passed. If it is not passed, the default remains that the UK will leave the EU at 23:00 GMT on 29 March.

The situation "is more fractious than ever", he adds.

Image source, AFP/ Getty Images

The prime minister has asked EU leaders for a delay to Brexit until 30 June.

She said the delay was a "matter of great personal regret", but insisted she would not be willing to extend Brexit any further than 30 June.

When asked at the summit if she would lead the UK out of the EU without a deal next week if her deal fails, she said: "What is important is that Parliament delivers on the result of the referendum and that we deliver Brexit for the British people.

"I sincerely hope that we can do that with a deal. I'm still working on ensuring that Parliament can agree a deal so that we can leave in an orderly way."

BBC News Channel

BBC Europe editor Katya Adler says that even if Theresa May gives promises to the EU 27, "they don't believe her".

"The trust for the prime minister is very, very low," she adds.

However, she notes that EU leaders are saying "what their populations want them to hear" when they are in front of the cameras.

Katya Adler says French President Emmanuel Macron is being "hard-line" because "he is aware of his domestic problems at home".

She suggests that his views might be more similar to Germany's Chancellor Angela Merkel "behind closed doors".

Image source, AFP/ Getty Images

The timings are estimates but here is how we expect the day to unfold:

• 14:30 GMT - Mrs May will make a short speech to the 27 EU leaders, making the case for a delay to Brexit
• The PM will then leave the room while the EU leaders decide whether to grant the UK's request and discuss other Brexit options
• 18:00 GMT - Press conference by European Council President Donald Tusk and European Commission President Jean-Claude Juncker. Mrs May is also expected to make a statement
• 18:30 GMT - Working dinner

Theresa May and other EU leaders are gathering in Brussels.

At the EU summit, the prime minister will try to persuade the other 27 countries to delay the UK's exit beyond 29 March.

Any delay to Brexit has to be agreed by all EU members.

The UK is set to leave the EU next Friday unless the law is changed. The current default position for leaving is without a withdrawal agreement.

So that's it from our live page for today. Before we go - here's a quick recap of what's been a very busy Brexit day!

• This evening, Theresa May spoke directly to the public over Brexit, telling them: "I am on your side."
• Speaking from Downing Street, the prime minister said people were "tired of infighting and political games" and it was "high time" MPs made a decision on the next steps.
• Earlier today, Mrs May wrote to EU Council President Donald Tusk requesting to delay Brexit until 30 June.
• She said the postponement was a "matter of great personal regret", and reiterated she would not be willing to extend Brexit any further than that date - despite appeals from some MPs for a longer extension to give time for a change in direction.
• Prior to Theresa May's speech this evening, President of the EU Council Donald Tusk said the EU would only agree to a short delay to Brexit if MPs approve the current withdrawal agreement next week.
• In the Commons, an emergency debate was granted to the shadow Brexit secretary Keir Starmer to discuss the government's plans to delay Brexit.