Syria has said the work of a team of UN chemical weapons investigators must wait until Wednesday. The foreign minister claimed that rebels had refused to guarantee the UN team safe passage.
Syrian Foreign Minister Walid al-Moallem said the UN investigations could not be conducted on Tuesday, blaming rebel forces for failing to promise not to attack the inspectors.
"Today, we were surprised by the fact that they were not able to get there because the rebels did not agree to guarantee the mission's safety," al-Moallem said at a news conference in Damascus. "So the mission has been delayed until tomorrow."
The opposition rejected al-Moallem's claims, saying the government was trying to convince the UN inspectors not to visit rebel-held areas.
The team conducted its first field analyses on Monday, at one point coming under sniper fire from unknown assailants.
"Following yesterday's attack on the UN convoy, a comprehensive assessment determined that the visit should be postponed by one day in order to improve preparedness and safety for the team," UN spokesman Farhan Haq said of the delay.
Haq gave no further details on why "confirmation of access" was not obtained on Tuesday, instead saying Secretary-General Ban Ki-moon "again urges all sides in the conflict to give safe passage and access to the team."
Hagel says the US is ready to act
US Defense Secretary Chuck Hagel said in a television interview on Tuesday, that if President Barack Obama ordered military action in response to an alleged chemical weapons attack in Syria, US forces would be ready to go just "like that."
"We have moved assets in place to be able to fulfill and comply with whatever option the president wishes to take," Hagel added in the BBC interview.
This came shortly after British Prime Minister David Cameron recalled parliament so that MPs can debate how the UK should respond to the alleged chemical weapons attack.
"Speaker agrees my request to recall Parliament on Thurs," Cameron said in a message posted on the micro blogging website Twitter. "There'll be a clear Govt motion & vote on UK response to chemical weapons attacks."
Earlier, the prime minister's spokesman said the British army would be prepared to take any action the government might ask it to.
"It's reasonable to assume our forces are making contingency plans," the spokesman said, while at the same time stressing that no political decision had yet been taken.
Syria warns against intervention
Earlier, Syria's Foreign Minister Walid al-Moallem used a Damascus press conference to deny that forces loyal to President Bashar al-Assad were behind last week's alleged attack using chemical weapons.
"I challenge those who accuse our forces of using these weapons to come forward with the evidence," al-Moallem said.
This appeared to in part be a response to a press conference US Secretary of State John Kerry gave in Washington on Monday, in which he accused the Syrian government of covering up a chemical attack.
Al-Moallem also pledged that Syria would not respond to any attack by foreign powers lying down.
"We have the means to defend ourselves and we will surprise everyone," he said. "We will defend ourselves using all means available. I don't want to say more than that."
msh, pfd/ph (Reuters, AFP, dpa, AP)