Syria’s foreign minister said Tuesday his country would defend itself using “all means available” in case of a U.S. strike, denying his government was behind an alleged chemical weapons attack near Damascus and challenging Washington to present proof backing up its accusations.

Walid al-Moallem spoke at a press conference in Damascus as condemnation of President Bashar Assad’s grew over last week’s purported attack with poison gas, which activists say killed hundreds of people. The Arab League threw its weight behind calls for punitive action, blaming the Syrian government for the attack and calling for the perpetrators to be brought to justice.

The announcement by the 22-member body, which is dominated by Gulf powerhouses Saudi Arabia and Qatar, provides indirect Arab cover for any potential military attack by Western powers.

The United Nations, meanwhile, said that its team of chemical weapons experts in Syria has delayed a second trip to investigate the alleged attack near Damascus by one day for security reasons.

Al-Moallem, speaking at a press conference in Damascus, likened U.S. allegations that President Bashar Assad’s regime was behind the attack to false American charges that Iraq possessed weapons of mass destruction before the 2003 U.S.-led invasion of that country.

“They have a history of lies — Iraq,” he said. Al-Moallem spoke a day after U.S. Secretary of State John Kerry said there was “undeniable” evidence of a large-scale chemical attack likely launched by Assad’s regime.

Kerry’s comments and tough language Monday laid out the clearest argument yet for U.S. military action in Syria, which, if President Barack Obama decides to order it, would most likely involve sea-launched cruise missile attacks on Syrian military targets.

U.S. Defense Secretary Chuck Hagel said Tuesday that U.S. forces are now ready to act on any such order.

In an interview with BBC television during a visit to the southeast Asian nation of Brunei, he said the U.S. Navy has four destroyers in the eastern Mediterranean Sea positioned within range of targets inside Syria. U.S. warplanes are also in the region, he said.

Support for some sort of international military response is likely to grow if it is confirmed that Assad’s regime was responsible for the Aug. 21 attack that activists say killed hundreds of people. The group Doctors Without Borders put the death toll at 355.

In an emergency meeting held Tuesday, the Arab League also called on members of the U.N. Security Council to overcome their differences and agree on “deterrent” measures against those who committed “this heinous crime.” The League said it will convene a meeting at the ministerial level next week to follow up on the situation in Syria.

“The council holds the Syrian regime totally responsible for this heinous crime and calls for all involved in the despicable crime to be given a fair international trial like other war criminals,” a statement issued by the League said.

Obama has yet to say how he will respond, but appeared to be moving ahead even as the U.N. team on the ground in Syria collected evidence from the attack.

Meanwhile, British Prime Minister David Cameron recalled Parliament on Tuesday for an urgent discussion on a possible military response, as the army drew up contingency plans.

Cameron’s office said that Britain is considering a “proportionate” response that would deter Assad from using chemical weapons in the future.

At the Syrian news conference, Al-Moallem called the U.S. accusations “categorically false.”

“I challenge those who accuse our forces of using these weapons to come forward with the evidence,” he said. Syria would fight back in case of a U.S. strike, he added.

“We have the means to defend ourselves and we will surprise everyone,” he told reporters in Damascus. “We will defend ourselves using all means available. I don’t want to say more than that,” he added.

Al-Moallem also rejected accusations that Syria was destroying evidence of the alleged attack. He said he was personally unconvinced that there will be international military action, but that if there was Syria could handle it.

“The strike will come and go. We get mortars every day and we have learned to live with them,” he said.

He also blamed the postponement of the U.N. team’s planned visit to the eastern Ghouta suburb on disputes between rebel gunmen who could not agree on safety guarantees for the investigators.

The U.N confirmed the one-day delay, saying only it was for security reasons. A statement said the decision was made Tuesday in order to improve preparedness and safety, after unidentified snipers opened fire on the team’s convoy on Monday on a similar trip to the region.

“The Secretary-General again urges all sides in the conflict to give safe passage and access to the team,” the statement said.

The U.N. team traveled Monday to the western Damascus suburb Moadamiyeh, one of the areas affected by purported chemical attack, where they collected samples and testimony after a treacherous journey through government and rebel-held territory. Their convoy was hit by snipers but members of the team were unharmed.

U.N. Secretary-General Ban Ki-moon said he had instructed U.N. disarmament chief Angela Kane in Damascus “to register a strong complaint” with both the Syrian government and opposition representatives for the convoy attack.

In Geneva, U.N. spokeswoman Alessandra Vellucci told reporters that the inspection team might need longer than the planned 14 days to complete its work and its priority now is to determine what chemical weapons might have been used in the Aug. 21 attack. “This is the first priority,” she said.

(AP)