British Prime Minister Theresa May stood firm on Thursday in the face of stinging domestic criticism, saying the UK and the European Union could overcome their "few but considerable" disagreements over Brexit.At the end of an inconclusive EU summit, May said there would be "tough negotiations" but declared that Britain and the bloc could strike a divorce deal that worked for both sides.EU Council President Donald Tusk said he, too, was more optimistic than after a bad-tempered EU summit last month and stalled negotiations last weekend."What I feel today is that we are closer to the final solutions and the deal," he told reporters.He acknowledged that "it may be a more emotional impression than a rational one. But emotions matter, also in politics."But May was under attack from across Britain's political spectrum after saying she's considering a European Union proposal that would keep the UK bound to the bloc's rules for more than two years after it leaves on March 29.Seeking to unblock Britain's stalled divorce talks with the EU, May said a proposed 21-month transition period for the UK after Brexit could be extended by "a matter of months."At present, the two sides say Britain will remain inside the EU's vast single market, and subject to the bloc's regulations, from the day it leaves until December 2020, to give time for new trade relations to be set up.EU Commission President Jean-Claude Juncker welcomed the opening, calling it "a good idea." And he added "this prolongation of the transition period probably will happen."The EU has said extending that period would give more time to strike a trade deal that ensures the border between Northern Ireland and the Republic of Ireland remains friction-free — the main sticking point in the Brexit talks.Yet the extension idea has angered pro-Brexit UK politicians, who saw it as an attempt to bind Britain to the bloc indefinitely.In an open letter on Thursday to May, leading Brexiteers accused the EU of "bullying" and said the border issue was being used as "a trap" by the bloc. The letter signed by former British Foreign Secretary Boris Johnson, ex-Brexit Secretary David Davis and other pro-Brexit Conservatives warned May not to "engage in a show of resistance and a choreographed argument followed by surrender" to the EU.Pro-EU politicians, meanwhile, said the proposal was another sign of May's weak bargaining hand and an attempt to stall for time. Liberal Democrat lawmaker Tom Brake said May was merely "kicking the can further down the road."Divorce talks between Britain and the bloc have stalled on the issue of the Irish border, which will be the UK's only land frontier with the EU after Brexit. Both sides agree there must be no hard border that could disrupt businesses and residents on both sides and undermine Northern Ireland's hard-won peace process. But each has rejected the other side's solution.The EU says the solution is to keep Northern Ireland inside a customs union with the bloc, but Britain rejects that because it would mean customs checks between Northern Ireland and the rest of the UK.Britain has proposed instead that all of the UK could stay in a customs union — but only temporarily. The EU insists there can be no time limit.With the deadlock, this week's summit, which had been billed as a make-or-break moment, turned simply into a chance for Britain and the EU to give themselves more time — perhaps until the end of the year — to break the logjam.German Chancellor Angela Merkel described finding a solution as "squaring the circle."But, she added; "Where there's a will, there should be a way, and normally there is a way."The lack of progress means a special EU summit on Brexit that had been penciled in for next month has been scrapped, though EU leaders said they would assess the situation later.The next official EU summit is scheduled for December, just over 3 1/2 months before Britain ceases to be an EU member. Any deal that is struck needs time to be approved by the British and European Parliaments.