MPs must debate and vote on the next steps of the Brexit process later, as Theresa May continues to try to reach an agreement through Parliament.
A series of amendments – intended to change the focus of Brexit – will be discussed during the debate, which should be a routine procedure.
But BBC editor Laura Kuenssberg said the prime minister may face another defeat.
Some Tory Brexiteers refuse to support the government, she said.
No 10 insists that Ms. May still plans to hold a vote on an agreement as soon as possible, but the Labor Party accused her of "wasting time" trying to "blackmail" the MPs so that they support his agreement.
The Prime Minister asked MEPs to approve a motion simply acknowledging that the process was ongoing and reaffirming their support for this approach.
But several MPs tabled amendments – which establish alternative plans – including a Labor Party that would force the government to return to Parliament before the end of the month to hold a substantive vote on the Brexit plan in the Commons.
Another representative of the SNP calls on the government to adopt a law to put an end to the Brexit process.
The Speaker of the House of Commons, John Bercow, has not yet determined which of these projects will actually be considered by members of Parliament.
However, influential figures in the research group of conservative backbench MPs from the European research group are unhappy to be invited to support the Prime Minister's motion.
This is due to the fact that the government should look for an alternative to the "backstop" with the support of a majority of deputies last month, with a separate initiative aimed at preventing the Brexit from taking place without a formal agreement.
The backstop aims to prevent the return of customs checkpoints to the Irish border in the event that no trade agreement enters into force.
Group vice-president Mark François told the BBC: "We can not vote for this because it is currently set up because it excludes any agreement and removes our bargaining power in Brussels".
He said the members had "pleaded" with Downing Street to change the wording, which he says is back to what the Prime Minister has previously told members.
"An important source of the ERG said that she had not yet decided to abstain or vote against it, but that she would not support the government," he said. said BBC political editor Laura Kuenssberg.
Most MPs want to avoid a scenario of non-agreement, fearing chaos in ports and disruption of business. But some Brexiteers downplayed this prospect, arguing that it was an example of "Fear Project".
MEPs rejected the deal negotiated with the EU by a historic margin in January and the prime minister said that she was seeking to make legally binding changes to the controversial "backstop" – the "police force". "Insurance" aimed at avoiding a return to border controls the Republic of Ireland.
The UK is currently due to leave the EU on March 29, whether or not an agreement has been approved by the Commons.
Could Brexit cause a split of work?
By the BBC political editor Laura Kuenssberg
You'll be used to people in my work saying things like, "These are critical days."
And hands in the air, on many occasions when a great movement is predicted, a wet bitch often happens to choke the waiting.
What I am going to say is perhaps a repetition of this familiar phenomenon. But I'm not the only person in Westminster this week to wonder if, after many, many months of private conversations during which this possibility was mentioned, in the coming weeks, or even in the coming days, is in fact critical will start to happen.
What happens next?
The prime minister promised to return to the House of Commons on February 26 with a new statement – triggering another debate and votes the next day – if an agreement was not found by that date.
If an agreement is reached, MEPs will have a second "significant vote", more than a month after the rejection of Ms. May's agreement in the first.
Ms May told MEPs on Tuesday that she was discussing a number of options with the EU to obtain legally binding amendments to support, including replacing it with " alternative arrangements ", a time limit during which he may remain in place or a unilateral decision. exit clause so that the UK can leave it at the time of its choice.
The EU has continued to say that it will not renegotiate the withdrawal agreement.
On Wednesday, the President of the European Council, Donald Tusk, tweeted that "no news is not always good news," saying that the EU was still waiting for "concrete and realistic proposals from London".
The Prime Minister also announced that she would waive the 21-day obligation prior to the approval of an international treaty, which means that she could postpone the final vote on the Brexit until a few days before the UK leaves the Union.
Former Attorney General Dominic Grieve warned on Tuesday that time was running out to ratify an agreement under the Constitution and Governance Reform Act.
The law requires 21 sitting days before ratification of any international treaty to allow MPs to study the agreement.
But Ms. May replied, "In this case, MPs will have already debated and approved the agreement in the context of a meaningful vote."
If there was not enough time for normal procedures, the government would amend the law around Brexit in order to allow its ratification more quickly.