The draft conclusions, however, have for now left the end date of the Brexit postponement blank before national European Union diplomats discuss them later in the evening in Brussels.
Such an extension would mean the United Kingdom having to take part in European parliamentary elections, which would be anathema to hardline Brexiteer Tories, and the country could be sidelined from budget decisions in Brussels.
The EU Council President - who published his letter with a tweet stating "there are times when you need to give time time" - wrote: "We should treat the United Kingdom with the highest respect, as we want to remain friends and close partners, and as we will still need to agree on our future relations".
The PM also updated Merkel on the ongoing discussions with the opposition Labour party.
Under the second plan, which kicks in if a deal is not passed by MPs, the European Union leaders could be asked to consider a nine or 12-month extension, until December 31 2019 or March 31 2020.
The main rebellion came from pro-Brexit Conservatives who want Brexit to happen sooner. "The public will not forgive the government if an extension is sought and agreed under the pretence of efforts to secure cross-party compromise", he said. Parliament has voted tonight against the damage & chaos that No Deal would cause for jobs, manufacturing, medicine supplies, policing & security.
The latest round of talks will include Mrs May's de facto deputy, Cabinet Office minister David Lidington, and Chancellor Philip Hammond from the Government side, with shadow Brexit secretary Sir Keir Starmer and shadow chancellor John McDonnell from Labour.
However, the prime minister has been warned by members of the 1922 committee of Conservative backbenchers that agreeing a customs union with the EU in Brexit talks would be "unacceptable".
But Jeremy Corbyn said he still doesn't know what concessions the Prime Minister is prepared to make.
And in Tuesday's Daily Telegraph, Tory grandee William Hague said the talks were "akin to having a dinner date with a crocodile".
Meanwhile, European Council chief Donald Tusk is pushing for the 27 member states to offer a one-year "flexible" extension to Article 50 - the mechanism that signals the date when Britain leaves the EU - instead.
Seibert would not further comment on the German government's position regarding May's Friday proposal to delay Brexit until June 30 to avoid crashing out without a deal at the end of this week.
The Cabinet Office said the elections would automatically be cancelled if the United Kingdom left before then.