EU foreign ministers in Luxembourg have put back the scheduled opening of talks on Turkey's EU membership bid, as attempts to break a deadlock continue.
Austria will not agree to talks without some changes
Talks were meant to start at 1700 (1500 BST), but were delayed over Austria's reservations about full Turkish entry.
No new time for talks was announced. The British EU presidency said a deal might not be reached on Monday.
Austria wants an alternative to full membership, but Turkey says it will not compromise on existing agreements.
A meeting to discuss starting entry talks with Croatia has been postponed.
Officials were planning to review Croatia's progress towards membership on Monday, but Mr Straw said it would have to wait until the problem over Turkey was resolved.
A British spokesman said as the Turkish delegation was waiting in Ankara for news of a breakthrough, it would be impossible for talks to start on time.
"The talks were scheduled for five o'clock. There's no plane in existence that can get the [Turkish foreign] minister [from Ankara] here for five o'clock," he told the AFP news agency.
But he added: "There has been real progress made."
Earlier UK Foreign Secretary Jack Straw said there were doubts that an agreement would be reached.
"I hoped that the outcome would be a conclusion with the arrival of a Turkish delegation to begin the accession conference later this afternoon, but that is by no means certain," he added.
Turkish Prime Minister Recep Tayyip Erdogan told Turkey's ruling AK party he would not compromise on the conditions for starting talks.
"We have protected and are continuing to protect our stance, which is appropriate to Turkey's national interests and political principles," he said, to loud applause.
The EU's member states must unanimously approve a negotiating mandate before talks with Turkey can begin.
At the centre of the crisis is Austria's insistence that the draft framework for entry talks should be rewritten, including the prospect of "privileged partnership", not just full membership, for Turkey.
Currently the draft text says only that full membership is the ultimate aim of any talks.
Public still coming to terms with last EU enlargement
Tabloid newspaper campaign against Turkish membership
Governing People's Party feeling vulnerable and isolated
Element of xenophobia and Islamophobia
Memory of Ottoman sieges of Vienna
The BBC's Jonny Dymond in Luxembourg says the Turks will not accept anything short of that and the other 24 member states have made it clear that they do not like the Austrian position.
He says there is some room for manoeuvre, but not much, and a chance that the EU is going to have to find another day to welcome Turkey into membership negotiations.
Turkey - a long-time associate EU member and a member of Nato - was given the green light to start negotiations nine months ago when the EU judged Ankara had met all the criteria.
The BBC's Istanbul correspondent Sarah Rainsford says the Turks see the deadlock now as a betrayal and there is immense frustration there.
Austrian Chancellor Wolfgang Schuessel has said he wants the EU to acknowledge popular concerns over its expansion.
Recent opinion polls suggest more than 70% of Austrians oppose full Turkish membership of the EU.
The predominantly Muslim country, with a population of 70 million, has had to meet strict criteria, including improving its shaky record on human rights, to begin accession talks.
Prime Minister Erdogan warned the EU must embrace its Muslim neighbour "or it will end up a Christian club".
His view was echoed by Mr Straw, who warned of a "theological-political divide, which could open up even further down the boundary between so-called Christian-heritage states and those of Islamic heritage".
If started, the Turkish negotiations are expected to take about 10 years.