(Adds senior U.N. official blaming Russian air strikes for pause in Syria peace talks)
By John Irish and Stephanie Nebehay
GENEVA, Feb 3 (Reuters) - Talks being mediated by the United Nations to end the war in Syria are on hold, U.N. envoy Staffan de Mistura said on Wednesday, while another official at the United Nations blamed the suspension on Russia's latest military escalation.
"I have concluded frankly that after the first week of preparatory talks there is more work to be done, not only by us but by the stakeholders," he said.
"I have indicated from the first day that I won't talk for the sake of talking."
He was speaking after meeting opposition coordinator Riad Hijab, who had just arrived in Geneva.
A senior U.N. official told Reuters on condition of anonymity that de Mistura called a halt to the talks after Russia increased air strikes to help the government of Syrian President Bashar al-Assad, undermining the negotiating process.
"I think the special envoy decided to suspend the talks because the (United Nations) did not want to be associated with the Russian escalation in Syria, which risks undermining the talks completely," the official said.
"The stepped up airstrikes gain the government ground, but also aim at humiliating the opposition on the ground and in Geneva," he added.
Hijab told reporters that it was not the last chance for peace, but the opposition would not return to peace talks without evidence of humanitarian improvements on the ground. The pause was a chance for the international community to put pressure on Assad and his allies, he said.
The pause came abruptly after several days of stuttering progress and postponed meetings, without De Mistura ever getting the two sides in a dialogue. De Mistura's office initially said the talks would resume on Feb. 25 but later issued a statement saying the could start again before that date.
It also came after intensified Syrian government advances backed by Russian air strikes on rebel positions in northern Aleppo.
Hijab blamed the Syrian government delegation for collapsing the talks, but its leader Bashar Ja'afari said it was "a failure of everybody except the government of the Syrian Arab Republic."
Ja'afari told reporters that he had known for "hours" that the opposition wanted to withdraw and accused De Mistura of pausing the talks to avert a walk-out.
"We consider that the style used by the Special Envoy to justify the withdrawal of Riyadh delegation under instructions from Saudi Arabia, Qatar and Turkey was not subjective. It didn't say the truth as it was," Ja'afari said.
Those regional powers, along with the United States, Russia Iran and others, comprise the "International Syria Support Group" (ISSG), which has thrown its weight behind De Mistura's initiative, without always agreeing on how he should go about it.
"We are waiting for the United States to stop leading from the back, and the Russians, who are co-broker of the ISSG, to stop adding fuel to the fire," said opposition spokeswoman Farah al-Atassi.
U.S. Secretary of State John Kerry and Russian Foreign Minister Sergey Lavrov and other top ISSG diplomats are expected to meet at the annual Munich security conference on Feb. 11.
"I will be asking for the ISSG to convene as soon as possible, hopefully in Munich, and for the U.N. Security Council to meet and reconvene on Feb. 25," De Mistura said.
German Foreign Minister Frank-Walter Steinmeier also said he saw an opportunity for negotiations at the Munich conference.
De Mistura said he planned to go to London for a Syria humanitarian pledging conference on Thursday, since the plight of Syria's 5 million refugees would be an additional incentive to reconvene the talks.
The Swedish-Italian diplomat apologised to reporters who had waited in sleet and hail while he spent 2 1/2 hours meeting the opposition delegation. He said he was neither frustrated nor disappointed by having to pause the talks.
"I have been long enough at the U.N. to know that when you have a five-year war that has had so many difficult moments you have to be determined but also realistic." (Reporting by John Irish, Stephanie Nebehay, Kinda Makieh, and Tom Miles; additional reporting by Louis Charbonneau in New York; Writing by Tom Miles; Editing by Hugh Lawson, Toni Reinhold, Grant McCool)
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