In Cyprus, Defense Minister Fotis Fotiou said naval traffic in the eastern Mediterranean was very heavy with vessels from "all the major powers." He also said Cypriot authorities were planning to deal with a possible exodus of foreign nationals from Syria.
U.S. military intervention in Syria was running into fierce opposition from some members of Congress. A growing chorus of Republican and Democratic lawmakers demanded that Obama seek congressional authorization for any strikes against the Assad regime.
Charles Heyman, a former British officer who edits The Armed Forces of the UK, said the lack of a U.N. Security Council resolution authorizing the use of force against the Syrian government greatly complicates matters for the West. He said that may make it difficult for Cameron to win parliamentary backing.
"It's clear the governments want some form of military operation, but if the Security Council doesn't recommend it, then the consensus is that it's plainly illegal under international law," Heyman said. "The only legal way to go to war is in self-defense and that claim is difficult to make."
Russia, a permanent member of the Security Council, has steadfastly opposed any international action against Syria.
Italian Foreign Minister Emma Bonino said her country would not back any military action against Syria unless it was authorized by the Security Council — even though it considers a chemical attack to be a war crime.
German Foreign Minister Guido Westerwelle said Monday that if the Syrian government were proven to have been behind the gas attack, then Germany would support "consequences." But with less than four weeks until national elections, it is unlikely Germany would commit any forces.
Center-left opposition parties have rejected military intervention without U.N. proof that the Syrian government was behind the attack. And a senior member of Chancellor Angela Merkel's party said the German military was already at "the breaking point" due to commitments in Afghanistan and elsewhere.