Kerry made a plea to the divided Syrian opposition on Thursday to attend the talks designed at establishing a transitional government in the country. The Syrian National Coalition is due to decide Friday whether to send representatives to the Swiss conference.
"On the eve of the Syrian opposition coalition general assembly meeting tomorrow to decide whether to participate in Geneva in the peace conference, the United States … urges a positive vote," the top US diplomat said in a speech from Washington.
"We do so knowing that the Geneva peace conference is not the end but rather the beginning," Kerry said, adding "this terrible conflict has taken many, many, many too many lives."
More than 100,000 people have been killed in Syria's 34-month civil war.
Kerry stressed the participation of Syrian opposition in the talks, dubbed Geneva II, was "the only way to bring about an end to the civil war that has triggered one of the planet's most severe humanitarian disasters and which has created the seeding grounds for extremism."
The opposition has demanded that peace talks lead to the end of President Bashar al-Assad's reign, while the government has said he may seek reelection. Kerry said both sides must agree on Syria's leader going forward, but that it cannot conceivably be Assad.
Iran will 'inevitably' participate
Speaking from Moscow on Thursday, Russian Foreign Minister Sergey Lavrov said Iran would "inevitably" attend the Geneva II talks. The role of Tehran - supportive of Assad's government - in the peace conference has thus far been unclear.
The US opposes Iranian involvement in the conference, but Lavrov reiterated Russian support for Tehran playing a role in Switzerland.
Iran "must be and inevitably will become part of the complex efforts to settle the Syrian problem," said Lavrov, who met with his Iranian counterpart Javad Zarif in Moscow. The two were later joined by Syrian Foreign Minister Walid al-Moallem.
Lavrov downplayed US concern that Russia is negotiating an oil deal with Iran, saying that there is "no hidden agenda" in the meeting between himself and his Iranian and Syrian colleagues.
"Russia, the Syrian people and Iran are interested in uprooting terrorism on Syrian territory," Lavrov said.
Weapons destruction delayed
Meanwhile, the head of the world's chemical weapons watchdog said on Thursday that the destruction of Syria's chemical weapons arsenal would likely be delayed until June because of logistics and security problems.
Ahmet Uzumcu, the head of the Organization for the Prohibition of Chemical Weapons (OPCW), said he was nonetheless "confident" that all the chemical weapons would be destroyed by June.
Syria already missed a December 31 deadline to have the most toxic substances sent to a port to eventually be destroyed at sea.
"As we were not able to meet the timeline for the 31st of December, from my point of view what is important is really the end of June 2014, so we will do our best to meet it," said Uzumcu.
dr/ph (AP, dpa, AFP, Reuters)