Syrian President Bashar al-Assad's regime deserves credit for complying with a chemical weapons deal, US Secretary of State John Kerry has said.
He was speaking after international monitors said the destruction of Syria's stockpile had begun.
The mission was established under a UN resolution, which was passed after a deal between Russia and the US.
The resolution followed international outrage at a chemical weapons attack near Damascus in August.
"The process has begun in record time and we are appreciative for the Russian co-operation and obviously for the Syrian compliance," Mr Kerry said after talks with his Russian counterpart Sergei Lavrov on the sidelines of the Asia-Pacific Economic Co-operation (Apec) summit in Bali, Indonesia.
"I think it's extremely significant that yesterday, Sunday, within a week of the (UN) resolution being passed, some chemical weapons were being destroyed.
"I think it's a credit to the Assad regime, frankly. It's a good beginning and we welcome a good beginning."
The destruction of Syria's chemical arsenal is being overseen by a team from the Organisation for the Prohibition of Chemical Weapons (OPCW).
An official on the joint OPCW-UN delegation said on Sunday: "The first day of destruction and disabling is over and missile warheads, aerial bombs, along with mobile and static mixing and filling units, were dealt with. Work continues tomorrow and in the next few days."
The actual destruction of the stockpile, being carried out by the Syrians, is not expected to be straightforward, as some sites are in combat zones.
It is the first time the OPCW - based in The Hague - has been asked to oversee the destruction of a chemical weapons armoury during a conflict.
The Syrian government gave details of its chemical weapons arsenal last month to the OPCW under the Russia-US agreement which also provided for Damascus to join the Chemical Weapons Convention.
That arsenal is thought to include more than 1,000 tonnes of sarin and the blister agent sulphur mustard among other banned chemicals.
In an interim report earlier this year, UN chemical weapons inspectors confirmed that the nerve agent sarin had been used in the attack in Ghouta on the outskirts of Damascus on 21 August.
It was estimated to have killed hundreds of people and was blamed by the United States and other Western powers on the regime of Bashar al-Assad. But he accuses Syrian rebels of being behind it.
Under the terms of the US-Russia deal, Syria's chemical weapons capability should be removed by the middle of 2014.
The speed with which the team has been able to reach the sites and start the process of destruction underlines the urgency of the mission, says the BBC's Anna Holligan in the Hague.
It was hoped that the new climate of co-operation would help bring about a wider conference in Geneva on ending the Syrian conflict.
UN-Arab League peace envoy Lakhdar Brahimi was quoted on French media on Sunday as saying he was encouraging all parties to come to Geneva in the second half of November but that peace talks were not a certainty.
Mr Assad denies that his forces had used chemical weapons, blaming the rebels instead.
More than 100,000 people have died since the uprising began in 2011 and millions more have fled Syria.