Theresa May did not say anything "substantially new" at a summit in Brussels, European Parliament President Antonio Tajani has said.
Mrs May addressed her 27 EU counterparts in a fight to keep the prospect of securing a successful Brexit deal alive.
"The tone was more relaxed than in Salzburg, undoubtedly," Mr Tajani said.
"There was a message of goodwill and readiness to reach an agreement, but I didn't perceive anything substantially new in terms of content as I listened to Mrs May."
Mr Tajani suggested that Mrs May was seemingly considering the option of extending the proposed 21-month transition period following Brexit to three years.
"Both sides mentioned the idea of an extension of the transition period as one possibility which is on the table and would have to be looked into."
An EU official said later that Mrs May had implied she was "ready to consider" a longer transition period.
During this time, the UK would remain subject to EU rules without being able to have any say on matters.
Prior to her speech, Mrs May had failed to rule out extending the Brexit transition period by 12 months as proposed by EU chief negotiator Michel Barnier on Wednesday.
Speaking to ITV News Europe Editor James Mates, the prime minister did not reject the possibility that the Brexit deadline could be extended.
"What we will be doing is looking at the issues that we need to address in relation to the backstop on Northern Ireland," said May.
"I believe it is possible by working together to find a resolution to that issue, and a resolution that ensures we are able to move forward with the full package, with the future partnership as well.
"Considerable progress has been made since Salzburg by working intensively over the next days and weeks, I believe we can achieve a deal - a deal that I believe everybody wants, and a deal that is in the interest of not just the UK but also of the EU".
Barnier had told the EU's 27 foreign ministers in Luxembourg that “more time” was necessary to come to an agreement on the UK's withdrawal and a resolution to the Irish border issue.
“We will take this time, calmly and seriously, to find this global agreement in the next weeks,” he said.
May's trip had been touted as “the moment of truth” in the challenging negotiations, amid growing concerns the UK and EU will struggle to agree over the Irish border problem.
The high-stakes discussions began on Wednesday with a diplomatic handshake and a kiss on the cheek from president of the EU's executive branch, Jean-Claude Juncker.
Meeting with Juncker was the first of many one-on-one meetings on the prime minister's agenda before she addresses her EU counterparts with hopes of bringing the negotiations to a close.
This Brussels meeting was when leaders of the 27 remaining member states were expected to agree to a special summit in November, in which the terms of Britain's withdrawal would be finalised - but hopes of this appear to be fading.
Speaking on Wednesday during Prime Minister's Questions, May insisted the government had made "good progress" on the future relationship with the EU when grilled by opposition leader Jeremy Corbyn.
"I expect the future relationship and intend to work on the future relationship to be in place by the first of January 2021," she said.
The prime minister was also forced to resist pressure from pro-Brexit backbenchers who are pushing her not to agree to any customs deal that could separate Northern Ireland from the rest of Britain.
"I made it clear earlier this year, have continued to make it clear and will carry on making it clear that we will not accept any proposals, which would effectively break up the United Kingdom," she said.
The negotiations had seemingly stagnated once again after Sunday's talks between Michel Barnier and Brexit Secretary Dominic Raab ended without an agreement.
May continues to face pressure from all angles - including from Tory Brexiteers - many of whom believe the prime minister is deliberately stalling negotiations in an attempt to encourage MPs to back her plan, rather than see the UK leave without a deal in place.