BRUSSELS, March 9 (Xinhua) -- After another week of no apparent progress on Brexit negotiations, EU chief negotiator Michel Barnier's latest attempts to assure London appear to have hit a wall by weekend.

After negotiations in Brussels that were characterized as "difficult", Barnier opened on Friday a series of tweets by noting that the bloc had proposed to Britain a "legally binding interpretation" of the Brexit withdrawal agreement.

Barnier also underlined an EU commitment "to give UK the option to exit the Single Customs Territory unilaterally," so long as the "backstop" along the Northern Irish border remained in place, to avoid a hard border that would go against the Good Friday peace agreements.

The "UK will not be forced into customs union against its will," Barnier insisted, while promising that the EU would continue "working intensely over the coming days to ensure the UK leaves the EU with an agreement."

In a rebuke, British Brexit Secretary Stephen Barclay tweeted that it was "not the time to rerun old arguments," with deadlines looming for Britain's departure from the EU on March 29.

Barclay appeared to dismiss the possibility of leaving the customs union while a "backstop" stays in place, an option that has been rejected by many Brexit advocates, and notably the Northern Irish Democratic Unionist Party, a part of the British government coalition, because it would mean separate rules for Northern Ireland and the rest of the United Kingdom.

BRITISH PM WARNS OF DEADLOCK

"We may not leave the EU for many months, we may never leave at all," British Prime Minister Theresa May warned British Members of Parliament in a Friday speech in the northern English town of Grimsby, as she tried to find support for the Brexit withdrawal agreement that she would put up for a vote at the House of Commons by March 12.

May said the agreement needed "just one more push" to get approved, but noted "If MPs do not back the deal, the only certainty would be uncertainty, months more spent arguing on Brexit."

Despite her warnings, signs are not positive that May has either found the assurances and concessions that many MPs want, or that she will drum up the support needed to have the agreement approved after it was defeated for the first time on Jan. 15.

Irish Prime Minister Leo Varadkar spoke to journalists Friday, dismissing Theresa May's speech, saying that the British PM needed "a change of approach" and London needed to come up with propositions if it wanted new concessions for the "backstop".

"What's not obvious is what the UK government is offering the European Union and Ireland should they wish us to make any further compromises," the Irish PM said, underlining "We have received no offer from them as to what they would give us in return for any changes."

"It requires a change of approach from the UK government to understand that Brexit is a problem of their creation," Varadkar said.

Dutch Prime Minister Mark Rutte echoed the sentiments of his Irish counterpart, saying that a breakthrough continued to appear elusive and required the UK to decide what it wanted, in order to make fresh proposals. Rutte also admitted he did not understand what Theresa May meant by "just one more push" was needed to reach a deal.

RROUTES TO BREXIT DELAY

Alongside Theresa May's attempts to rally support for her Brexit deal, a voting calendar has been set by her government to soothe divisions within the British conservative party and script how decisions will be made leading up to March 29.

The government has committed to putting the withdrawal agreement to a vote in the House of Commons by March 12, with whatever final concessions May is able to receive from the EU. Having lost her original attempt in January by 230 votes, and not having come back to Westminster with significant changes or assurances on the Northern Irish "backstop", the British PM might be snubbed again.

If the deal is rejected by MPs, they will have the opportunity to vote by March 13 on whether they would accept a no-deal Brexit. Given the wide negative publicity of consequences associated with no-deal Brexit, it is also considered to be unpopular.

If a no-deal Brexit is rejected, MPs will be able to vote by March 14 on whether Britain should attempt to negotiate a delay of Brexit, though not on the extend of that time period. May has already said that any extension should be a one-off, and no longer than until the end of June, a prospect she has stated is not her preference.

European Council President Donald Tusk said in February that "an extension would be a rational solution," but European leaders are looking for good reason.

French President Emmanuel Macron has already indicated that an extension needed justification. The French Minister for Europe Nathalie Loiseau reiterated her president's stance Thursday in London, telling journalists "A short extension: why not, if there is a good and credible reason."

European Parliament President Antonio Tajani did not think that Brexit could be delayed by more than "a maximum of several weeks". He said in an interview published Saturday with Germany's Funke group of newspapers that London would have to justify an extension, such as wanting time to hold new elections or a new referendum.

The European Parliament president expressed a common position in Europe, however, that the responsibility for what happened next remained with Britain. "They've decided to leave - it's their problem, not ours," Tajani said.