The Turkish Cypriot chief negotiator has accused the Greek Cypriots of delaying tactics and suggested reunification talks should be ditched.
Kudret Ozersay was speaking in London days after the UN Secretary-General Ban Ki-moon cancelled plans for a multilateral conference on Cyprus.
The island's north became separate in 1974, when Turkish forces invaded in response to a Greek-led coup.
The Republic of Cyprus accuses the Turkish Cypriots of negative tactics.
The two sides remain divided over property, the right of return of the displaced and security.
Cyprus President Demetris Christofias said that since May 2010, when Dervis Eroglu became Turkish Cypriot leader, "serious backtracking is being noted in the talks".
He said Turkey and the Turkish Cypriots were "in reality promoting a two-state solution".
Mr Ozersay denied the "backtracking" allegation and also denied Cyprus's claim that Turkey was manipulating the Turkish Cypriot negotiators.
Mr Ozersay said the Turkish Cypriot negotiators were "exhausted" and he felt the talks were going nowhere because of Greek Cypriot intransigence.
Mr Ozersay, a professor of international law since the talks began in 2008, said the Republic of Cyprus had no incentive to find a comprehensive settlement because it had already been accepted into the EU, but he added: "The status quo is killing us".
Correspondents say the UN had wanted both sides to resolve outstanding issues before Cyprus takes up the presidency of the EU in July.
A UN peacekeeping force has been deployed on the island since 1964.
The Republic of Cyprus joined the EU in 2004, despite the frozen conflict with the breakaway Turkish-controlled north of Cyprus.
The self-declared Turkish Republic of Northern Cyprus (TRNC) is only recognised by Turkey.
A fresh start?
The continuing dispute is a major obstacle blocking Turkey's efforts to join the EU.
President Christofias is facing elections next year but Mr Ozersay said he did not believe that was the main reason for the "lack of political will" on the Greek Cypriot side, which he claimed had led to the "deadlock".
Mr Ozersay insisted the only issue Ankara was interested in was external security and the role of the Turkish armed forces and he said this had not even been discussed yet in the talks.
He said the idea of a "Cypriot-led solution" had clearly failed after four years of talks and it was time to start again, perhaps with an independent, neutral power who could lead both sides to an agreement.
"We are exhausted. Neither side believes we will be successful," Mr Ozersay said.
"Opinion polls on both sides say people do not believe a comprehensive settlement will be reached, even though those same polls say people want there to be a settlement.
"If the Greek Cypriot side does not give their consent for a multilateral conference then the Turkish Cypriots will not give consent for the current process to continue."
Asked if he felt the Greek Cypriots were "dragging their feet" he said: "Yes."
Mr Ozersay said he was committed to a one-state solution and it was "not helpful" to speculate about the possibility of the "Taiwanisation" of Cyprus - whereby the so-called TRNC simply goes around the world seeking diplomatic recognition.