Syria's government and the United Nations have agreed on an immediate UN probe into allegations of chemical weapons use near Damascus last week, as Russia warned against assigning blame for the attack "too soon."
The deal was concluded in Damascus between the Syrian government and the UN's high representative for disarmament, Angela Kane.
Damascus said the agreement is "effective immediately" and will give the green light to UN investigators who are already on the ground in Syria. The UN said the investigation is expected to start on August 26.
Russia's Foreign Ministry, meanhwile, warned the West against preempting the results of the probe.
Ministry spokesman Aleksandr Lukashevich said in a statement, "We urge those who, by attempting to impose their own results on the UN experts, are raising the possibility of a military operation in Syria to use their common sense and refrain from committing a tragic mistake."
The statement warned that any unilateral military action in Syria would undermine efforts for peace and have a "devastating impact" on the security situation in the Middle East.
An unnamed senior U.S. government official said there was "little doubt" that the government of President Bashar al-Assad was behind the attack.
The official accused Syrian authorities of intentionally delaying the UN probe "in order to facilitate the degradation of evidence of their use of chemical weapons."
Opposition activists say as many as 1,300 civilians were killed on August 21 in the chemical weapons attack by government forces in the Damascus suburb of Ghouta.
The Syrian regime has repeatedly denied accusations that it was behind the attack. Information Minister Omran Zoabi told Lebanese television on August 24 that there was evidence rebels had used the weapons.
"We are not trying to defend ourselves from accusations that we did or did not use them. We are assuring you that we did not use them," he said. "But we also want to say that those who have used this weapon are terrorist armed groups, and as you know we have evidence and information, not to mention the satellite imagery that our Russian friends have talked about, as well as facts on the ground, and there are people suffering as a result of this. They are witnesses to its usage."
On August 24, U.S. President Barack Obama met with his national security team to assess the situation and consider a U.S. response.
Defense Secretary Chuck Hagel has said Obama told the Pentagon "to prepare for all contingencies."
In a separate development, Syria's state news agency SANA said the governor of the restive province of Hama, Anas Abdel-Razaq, was killed in a car bombing on August 25 by "terrorists" -- a term used by state media to refer to rebels fighting to oust Assad.
More than 100,000 people have been killed in the 29-month conflict, with at least 2 million Syrian refugees pouring into neighboring countries.
With reporting by Reuters, AP, dpa, AFP, and the BBC