US Defense Secretary Chuck Hagel said the United States was "ready" to launch a strike on Syria if President Barack Obama chose to order one.
"We have moved assets in place to be able to fulfill and comply with whatever option the president wishes to take," Hagel told the BBC on Tuesday.
When asked if the US military was prepared to respond just "like that," Hagel replied, "We are ready to go, like that."
On Monday, Secretary of State John Kerry said there was "undeniable" proof of chemical weapons attacks in Syria and called the targeting of civilians a "moral obscenity."
The United States said it will share evidence of the Syrian government's chemical weapon use in the coming days.
"I think the intelligence will conclude that it wasn't the rebels who used it, and there'll probably be pretty good intelligence to show ... that the Syria government was responsible," Hagel said.
"I think most of our allies, most of our partners, most of the international community that we've talked (to) — and we have reached out to many — have little doubt that the most base, human, international humanitarian standard was violated in using chemical weapons against their own people."
United Nations & Arab League
Chemical weapons inspectors from the United Nations were shot at on Monday as they tried to investigate the site near Damascus where Syrians were allegedly attacked with chemical weapons on Aug. 21, leaving an estimated 500 to 1,800 dead.
The UN team delayed a second trip to the site of a different alleged attack on Tuesday, in order to improve safety measures. "Considering the complexities of the site, confirmation of access has not been obtained but is expected later today," the UN said in a statement.
The Arab League, after holding an emergency meeting on Tuesday, blamed Assad's regime for the alleged chemical weapons attack and called on the UN Security Council to respond to "this heinous crime."
The Syrian opposition was informed that Western powers would strike Syrian President Bashar al-Assad's forces within days, according to sources who were present for a meeting between envoys in Istanbul.
A source told Reuters, "The opposition was told in clear terms that action to deter further use of chemical weapons by the Assad regime could come as early as in the next few days, and that they should still prepare for peace talks at Geneva."
Meanwhile, Syria's foreign minister Walid al-Moallem responded to suggestions of a strike, saying his country would defend itself using "all means available."
Speaking in Damascus on Tuesday, al-Moallem challenged Kerry's assertion that the Syrian regime had used chemical weapons, calling for proof.
The United States' ally Britain has also started making plans for military action in Syria, with Prime Minister David Cameron returning to London early to deal with the crisis.
On Twitter, Cameron said there would be a clear government motion and vote on the UK's response to the chemical weapons attacks.
Germany said it would consider responding with force after being faced with "very clear evidence that this was a chemical weapons attack," though Chancellor Angela Merkel urged a political solution.
France's foreign minister said Monday that the decision on whether to use force would be made in the coming days. "The options are open. The only option that I do not envisage is to do nothing," said Laurent Fabius.
Russia, one of the Syrian regime's few remaining allies, sent out a warning on Tuesday. It said that any military action on Syria could cause "catastrophic consequences" for the region and asked the international community to show "prudence."
"Attempts to bypass the Security Council, once again to create artificial groundless excuses for a military intervention in the region are fraught with new suffering in Syria and catastrophic consequences for other countries of the Middle East and North Africa," foreign ministry spokesman Alexander Lukashevich said.
"We are calling on our American partners and all members of the world community to demonstrate prudence (and) strict observance of international law, especially the fundamental principles of the UN Charter," he continued.
China's official news agency Xinhua called the Western response to developments "irresponsible and dangerous," saying that recent rhetoric indicated "they have put the arrow on the bowstring and would shoot even without a UN mandate."
While Reuters noted that Xinhua's commentaries are not official statements, they do reflect the thinking of the Chinese government.