Washington denied claims by Syria's foreign minister on Saturday that American diplomats had sought to negotiate directly with their Syrian counterparts at last week's 'Geneva 2' peace conference in Switzerland.

State Department spokeswoman Jen Psaki said the US had offered to connect with Syrian officials "on a staff level" through the UN and Joint Special Representative Lakhdar Brahimi.

"At no point did the United States offer to negotiate directly with the Syrian regime," she said, adding that the US had made similar offers throughout the conflict.

Psaki was responding to a query from Reuters after Syrian Foreign Minister Walid Al-Moualem said the Americans had requested direct negotiations in Montreux, the Swiss city where talks began on January 22 before moving to Geneva.

"We refused to do so before Secretary of State John Kerry apologises for what he said at the conference," Moualem told reporters aboard the Syrian government delegation's flight back to Damascus.

In the comments published by Syria's national news agency Sana, Moualem did not specify what Kerry had said that required an apology.

But Psaki said such a gesture would not happen.

"At no point will Secretary Kerry ever apologise for speaking the truth about the brutality the Assad regime has inflicted on the people of Syria," she said.

A contentious week-long first round of talks began with uncompromising speeches, by Kerry and Moualem among others, and repeatedly seemed on the verge of collapse before the two sides even entered the same room.

The conference adjourned on Friday with no progress towards ending the civil war and the government unable to say whether it will return for the next round of negotiations beginning on February 10.  - Reuters