Russia has backed Syria as acting in good faith to eliminate its chemical weapons, after the US accused the government of Bashar al-Assad of stalling the plan due to end in June.
Mikhail Ulyanov, a Russian diplomat, was quoted by the Interfax news agency on Friday as saying that there was no need for additional pressure on Damascus over the destruction of its stockpiles.
"We see that the Syrians are approaching the fulfilment of their obligations seriously and in good faith," he said.
The comment came after the US said just four percent of Syria's declared chemical stock has been eliminated.
Efforts to remove these materials from Syria have "seriously languished and stalled", said ambassador Robert Mikulak in a statement to the Organisation for the Prohibition of Chemical Weapons (OPCW) on Thursday.
"Syria must immediately take the necessary actions to comply with its obligations under the Chemical Weapons Convention, Executive Council decisions, and UN Security Council Resolution 2118," said Mikulak, the US permanent representative to the OPCW.
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US Secretary of State John Kerry reiterated the tough US stand on the issue, saying that Syria had no excuse for delays in ridding itself of chemical weapons, and urged it to move 'very rapidly' to allow them to be shipped out of the country.
"Every indication we have is that there is no legitimate reason why that (removal) is not happening now," Kerry told a news conference in Berlin.
"We want the Syrian regime to live up to its obligations and it is critical that very rapidly all those chemical weapons are moved from their 12 or so sites to the one site in the port (of Latakia) to be prepared for shipment out of Syria."
Timelines adopted last year required that 100 percent of "priority one" chemicals be eliminated by December 31, 2013, while the deadline for removing "priority two" chemicals is Feburary 5. That deadline will also not be met.
The Syrian government has attributed the delays to "security concerns", saying it needs additional equipment to ensure their safe transportation - a claim Mikulak rejected.
"Syria's requests for equipment and open-ended delaying of the removal operation could ultimately jeopardise the carefully timed and coordinated multi-state removal and destruction effort," he said.
During a visit to Poland on Thursday, US Defence Secretary Chuck Hagel also criticised Syrian efforts, saying he has asked his Russian counterpart to put pressure on Damascus to comply with the deal.
Peace talks continue
Meanwhile, peace talks between the Syrian government and the opposition have ended without a breakthrough in the Swiss city of Geneva.
The talks have made slim progress, but have raised hopes for a solution to the country's civil war, UN Arab League envoy to Syria, Lakhdar Brahimi, told reporters after a week of closed-door negotiations.
The UN mediator said on Friday that he saw some positive steps and common ground, but the gaps between the sides "remain wide".
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He said that rival Syrian delegations could return for a second round of peace talks on February 10, to build on the "modest beginning".
The Syrian opposition has said that President Bashar al-Assad must leave power, while the government has said that his role was not up for debate.
Syria's opposition spokesman, Louay Safi, told Al Jazeera: "There is no way there could be progress without establishing a governing transitional body with authority to deal with political and military matters."
Syria's Foreign Minister Walid Muallem said that the UN-brokered peace talks failed to achieve any tangible results.
"I regret to tell you that we have not reached tangible results during this week," he told reporters after the end of talks.
Source: Al Jazeera and agencies