The European Council President Donald Tusk also struck a similar tone on Monday, tweeting: "We will not renegotiate the deal, including the backstop, but we are ready to discuss how to facilitate United Kingdom ratification".
The problem centres on an insurance policy known as the backstop, created to guarantee an open Irish border.
Both May's ruling Conservatives and the main opposition Labour Party have pledged to implement the results of the 2016 referendum in which British voters backed exiting the European Union 52 percent to 48 percent.
May didn't say what the solution might be, noting that "we are just at the start of the negotiations and the start of the discussions".
If British lawmakers approve the agreement, it must still be endorsed by European Parliament members before March 29.
On 25 November, the European Council approved the agreement on Britain's withdrawal from the EU and agreed to ensure the entry into force of the Treaty on Brexit, on 30 March 2019.
Asked if she had been informed the 48-letter requirement was met, the prime minister said: "No, I have been here in Europe dealing with the issue I have promised Parliament I would be dealing with".
A minor mishap for British PM Theresa May as a vehicle door wouldn't open in Berlin. Scottish First Minister Nicola Sturgeon said her Scottish National Party would support an attempt to topple the government and trigger a new election. He added that with the canceled vote in London "we have spiraled again into a new mess".
May has repeatedly ruled out a second public vote, but could face pressure to call one if Britain slips into political paralysis.
This was stated by the speaker of the house of Commons of the Parliament John bercow, according to British media.
Legendary anti-war activist and former British parliamentarian George Galloway joined Radio Sputnik's Loud & Clear Monday to discuss the British political scene.
France's European Union affairs minister, Nathalie Loiseau, on a visit to Brussels, suggested her country's president, Emmanuel Macron, would urge the EU's leaders at a summit starting on Thursday to take responsibility for their own preparations rather than be sucked into May's domestic political drama.
The EU reacted coolly, with European Council President Donald Tusk saying it was ready to discuss how to smooth ratification but that neither the withdrawal agreement nor the Irish backstop would be renegotiated.
"There is no room whatsoever for renegotiation but of course there is room, if used intelligently, to give further clarification and further interpretations", he said.
"As a result, if we went ahead and held the vote tomorrow, the deal would be rejected by a significant margin", she said.
Commons Leader Andrea Leadsom suggested Mrs May was seeking changes that would give Parliament an additional "democratic ability to decide".
May said she wanted to seek assurances from European leaders that the backstop would be a last resort, and if it were to be invoked, it would be temporary.
"We spent so much time, energy and creativity to negotiate something we in Berlin and Brussels don't want".
He confirmed he would meet Mrs May on Tuesday evening but reiterated: "The deal we have achieved is the best deal possible - it is the only deal possible".
"Our responsibility is to prepare for a no deal because it's a hypothesis that is not unlikely", Nathalie Loiseau said.