* Mediator says talks "laborious"
* Rival sides have nothing new to report
* Obama chides Moscow over Syria stance
* Syrians questioning men allowed to leave Homs (Adds U.S. State Dept. comment, paragraphs 13-14; U.S. intelligence chief, 25-27)
By Oliver Holmes and Khaled Yacoub Oweis
GENEVA, Feb 11 (Reuters) - Peace talks between the Syrian government and opposition are not making much progress, the international mediator said on Tuesday after a face-to-face meeting of the warring parties in Geneva that both sides called fruitless.
Negotiations intended to end Syria's three-year-old civil war began with a week-long session last month and have resumed this week in Geneva. There had been hopes for Tuesday's talks after they began with a minute's silence for the 130,000 people killed since the conflict began.
But Lakhdar Brahimi, a veteran diplomat charged with running the internationally sponsored talks, told a news conference the second round so far was as "laborious" as the first. "We are not making much progress," he said.
Syrian Deputy Foreign Minister Faisal Mekdad said Tuesday was a "lost day" while opposition spokesman Louay Safi said "no progress" had been made.
The talks have been held up over the agenda, with the opposition wanting first to discuss plans for a transitional government, and the government insisting the first issue must be fighting terrorism - a word it uses for all armed rebels.
In an attempt to break the deadlock, Brahimi had proposed that they use Tuesday to discuss ending the violence and Wednesday to raise formation of a transitional governing body.
But both sides said the agenda had still not been agreed.
"Today was another lost day because the representatives of the Coalition insisted that there is no terrorism in Syria," Mekdad said of the opposition stance.
National Coalition spokesman Safi said: "It is obvious the regime is stalling and still believes in a military solution."
Anas Abdah, a strategist in the opposition team, said: "The regime is consistently trying to get rid of the transitional governing body. Today it basically refused to discuss it."
The opposition believes a transitional administration must exclude Syrian President Bashar al-Assad. The government will not discuss his leaving.
A statement from the Coalition said the session was very tense and accused the government of attempting to stall.
At a news briefing in Washington, U.S. State Department spokeswoman Jen Psaki said no one had expected the talks to be easy.
"We don't expect a major breakthrough this week. And what we believe we need to continue to do is press the regime, gather the international community, press the regime to engage more seriously in this process," Psaki said.
OBAMA CHIDES RUSSIA
The talks are sponsored by the United States, which supports the opposition, and Russia, which backs Assad. The powers have largely blamed each other for the intransigence of their allies.
U.S. President Barack Obama suggested that Moscow - which has used its Security Council veto to block U.N. resolutions against the Damascus government - was to blame for preventing action that might help protect and aid vulnerable civilians.
Referring to U.S. Secretary of State John Kerry, Obama said: "Secretary Kerry and others have delivered a very direct message to the Russians that they cannot say they are concerned about the well-being of the Syrian people when there are starving civilians."
So far, the only tangible result of the talks process has been an agreement to allow aid to enter and people to leave the old city of Homs, under government siege for more than a year.
United Nations officials said Syrian authorities had detained 336 men who had left Homs for questioning, raising concerns about their welfare.
"A number of boys and men and their families were seized by the authorities as they left the besieged area. It is essential that they do not come to any harm," said Rupert Colville, spokesman for the U.N. human rights office.
Those held, deemed to be of fighting age by the Syrian authorities, were among 1,151 who left the old city during a ceasefire extended for a second three-day period on Monday.
The United Nations said 41 of the men had been released. The governor of Homs said 100 had been freed. The rest were being questioned in a school, under the "general monitoring" of U.N. staff, a U.N. spokeswoman said. Of five heavily pregnant women evacuated, one had since given birth.
Those leaving were very weak, with signs of malnutrition, said a World Food Programme spokeswoman. Survivors recounted a daily diet that included leaves and grass.
The United Nations says it does not know how many people are still in old Homs - just one of the many sieges that have trapped more than a quarter of a million Syrians.
At a U.S. Senate hearing on Tuesday, National Intelligence Director James Clapper said he was convinced that documents alleging torture and murder in the Syria conflict were authentic.
Clapper was asked during the hearing whether he had seen the documents, published by CNN and other media, as potential proof of atrocities by Syria's government. He said he had, and that he believed they were real.
"They're terrible. And when you consider the humanitarian disaster in addition to the 2.5 million refugees, the 6.5 million or 7 million that are internally displaced, the 134,000 plus people that have been killed, it is an apocalyptic disaster," Clapper said. (Reporting by Stephanie Nebehay, Tom Miles and Erika Solomon, and Patricia Zengerle in Washington; Writing by Giles Elgood and Peter Graff; Editing by David Stamp, Alastair Macdonald and Gunna Dickson)