Syria's warring sides on Friday admitted there was "no progress" in breaking through the deadlock in their faltering peace process, as doubts increased that international pressure could save the talks from collapse.

On what was expected to be the last day of the current round of the UN-brokered peace talks, there was no sign that rival negotiators would even sit down in the same room, something they have done just twice since the session began on Monday.

"We deeply regret that this round did not make any progress," Syria's deputy foreign minister, Faisal Muqdad, said after meeting with UN mediator Lakhdar Brahimi.

He told reporters the Syrian government wanted a "political solution" but "the other side has come with a different agenda".

Separately, opposition spokesman Louay Safi complained about the regime's failure to budge.

"The negotiations have reached an impasse," Safi said.

"It means that the negotiations are not moving towards a political solution. We are now awaiting serious progress," he told reporters.

Just as they did during the debut round of talks in January -- the biggest international push so far to end the war in Syria -- the foes have this week sparred over what should top the agenda, which blocked any possible negotiation.

January's round failed to bear fruit, beyond the simple fact of getting the warring sides to the table for the first time in the three-year conflict that has claimed over 136,000 lives and driven millions from their homes.

The opposition insists the focus must be on shifting Syria from one-party rule under President Bashar al-Assad.

But government negotiators refused to discuss a 24-point opposition proposal set out this week for a so-called Transition Governing Body to halt violence and pave the way for elections.

- Trading 'terrorism' barbs -

The regime insists Assad is not up for debate and wants the talks to focus on "terrorism" -- the label applied to the revolt which it says has been fuelled by foreign jihadists and Gulf money.

"We are willing to discuss the question of the Transitional Governing Body once we have reached an agreement on fighting terrorism," Muqdad said.

Pressed on whether there was a difference between the jihadist militias and the moderate Free Syrian Army, Muqdad was unequivocal.

"Those who carry arms against their people and government are terrorists," he said.

The opposition rejects such arguments, underlining that the Free Syrian Army is itself battling Al-Qaeda-linked fighters.

It also accuses the Damascus regime of terrorism by raining "barrel bombs" onto opposition-held communities, and deploying Iranian Revolutionary Guards and the Iranian-backed Lebanese Shiite militia Hezbollah, considered a terrorist group in the West.

"We have no problem discussing terrorism. Terrorism has been instigated by the regime," Safi said.

- 'In a dead end' -

Observers said the talks were hanging in the balance.

"We are in a dead end," said a Western diplomat, warning the prospects looked "grim" and that it would be tough for Brahimi to organise a third round.

The so-called Geneva II process was initiated by the United States, which backs the Syrian opposition coalition, and Moscow, which supports the government.

In an effort to inject life into the talks, they sent top envoys to Geneva this week.

But after a meeting with high-ranking US and Russian diplomats Thursday, Brahimi admitted that "failure is still staring us in the face".

While the opposition has said Russia is clearly not wedded to Assad, Muqdad said Moscow and Damascus "agreed on how to succeed".

Safi said the opposition was appealing to the international community to "make a difference to push this process forward" but that a "pause" looked likely in the meantime.

Algerian veteran peacemaker Brahimi, who helped broker past deals in Lebanon, Afghanistan and Iraq, has pledged not to "leave one stone unturned if there is a possibility to move forward".

But the Western diplomat cautioned: "I would not assume he will stay indefinitely," saying Brahimi might have "concerns about his own credibility" if he allows the process to continue like a broken record.

- Death toll mounts -

Meanwhile, regime air attacks and fighting have sent the death toll in Syria soaring, with 236 people killed on average each day since the talks began in January, the Syrian Observatory for Human Rights said Thursday.

The ongoing evacuation of civilians from besieged rebel-held areas of Homs -- seen as the only tangible result so far -- has been hailed as a relative success.

But UN humanitarian chief Valerie Amos expressed frustration at the "extremely limited and painstakingly slow" process of getting 1,400 people out, given that 250,000 are under siege across Syria.

Muqdad had sharp words for Amos, accusing her of an "unacceptable" failure to recognise that there was "terrorism" in Syria and that it hindered aid operations.

The United Nations said Friday 381 male evacuees from Homs -- 14 of them boys aged under 18 -- were still in regime hands as part of its "vetting" process.

The regime has said it was essential to interrogate men in order to weed out "terrorists", but the opposition said separating the men from women and children was ominous.