U.S. Vice President Joseph Biden (center) gestures as he arrives on the second day of the 49th Munich Security Conference on Feb. 2, 2013 in Munich as world leaders, ministers and top military gather for talks with the spotlight on Syria, Mali and Iran. (CHRISTOF STACHE/AFP/GETTY IMAGES)

A top Syrian opposition leader’s offer to engage in talks with the Syrian government drew praise Saturday from both the United States and Russia, bringing a rare moment of unity to the contentious global debate on the country’s future.

Syrian opposition chief Mouaz al-Khatib met separately Saturday with Vice President Biden and Russian Foreign Minister Sergey Lavrov on the sidelines of a security conference here, a day after Khatib reiterated his readiness to hold talks with Syrian President Bashar al-Assad, provided certain conditions were met.

In his one-on-one meeting with the cleric, Biden’s office said, the vice president commended the move, the first time a major ­Syrian opposition leader has raised the possibility of direct talks with Assad, but he made no new promises of support for the opposition.

Before meeting with Khatib, Biden in a speech at the conference said, “President Assad, a tyrant, hellbent on clinging to power, is no longer fit to lead the Syrian people, and he must go.” He also met separately with Lavrov and the joint U.N.-Arab League special envoy to Syria, Lakhdar Brahimi.

Lavrov, meanwhile, said he was happy to hear Khatib’s offer.

“We expressed interest in regular contacts” with the Syrian opposition, Lavrov told journalists aboard his plane back to Moscow, Interfax reported. The offer of talks “was a very important move,” Lavrov said. “Realism has taken the upper hand.”

U.S. and Russian officials have battled over the conflict in Syria, which has claimed more than 60,000 lives since it began nearly two years ago, according to U.N. estimates. Russia has staunchly blocked attempts to condemn Assad in the U.N. Security Council, making the joint embrace of the possibility of talks even more unusual.

Khatib, who heads the Syrian Opposition Coalition, posted his offer on his Facebook account Wednesday and repeated it late Friday at the conference.

“As a gesture of goodwill,” Khatib said Friday, “we are ready to sit at the negotiation table with this regime.” But his preconditions, including a demand that Assad free 100 political prisoners, seemed unlikely to be met, and the Syrian opposition is far from unified about talks with the government.

In their meeting, Biden urged Khatib to continue to encourage unity in the movement, the vice president’s office said.

The offer of talks came as Brahimi made some of his most pessimistic comments yet about the prospects of an end to the conflict in Syria.

“I am much more conscious of the difficulties and . . . the country being broken down day after day, than I am of a solution,” he told the conference Friday, speaking on a panel alongside Khatib.

Separately, Biden said Saturday that the United States is prepared to engage in direct talks with Iran over its controversial nuclear program, although he added that the administration would negotiate only if Iranians were “serious.”

Talks have been offered in the past, but they have never materialized, and last month Iran defiantly said it planned to accelerate its enrichment of uranium. Biden said that it was not too late to reach an agreement on Tehran’s nuclear ambitions.

“Our policy is not containment,” the vice president told the gathering of security officials and world leaders in Munich. “It is to prevent Iran from acquiring a nuclear weapon.”

During a hectic weekend of diplomacy in this elegant German city, Biden and Iranian Foreign Minister Ali Akbar Salehi were in the same building at the same time, but they did not meet. One-on-one contact, Biden said, could take place only after American officials are convinced that negotiations would be fruitful.

“The ball is in the government of Iran’s court,” Biden said. Talks can happen if their aims are “real and tangible, and there has to be an agenda that they’re prepared to speak to,” he added. “We are not just prepared to do it for the exercise.”

He set no timeline on the offer.

President Obama’s nominee for defense secretary, Chuck Hagel, on Thursday at a Senate confirmation hearing said he supported “the president’s strong position on containment,” a comment on which he soon backtracked and which Biden’s comments on Saturday appeared designed to clarify.

Biden also said Saturday that the United States strongly supported France’s intervention in northern Mali, undertaken to push back the spread of Islamist militants with ties to al-Qaeda in the Islamic Maghreb, or AQIM. Washington has offered logistical support to the French but has not taken part in combat.

The fight against militants “will take a comprehensive approach, employing the full range of tools at our disposal, including our military,” Biden said. “The fight against AQIM may be far from America’s borders but is fundamentally in America’s interest.”