The United States and France say international support is growing for military strikes to punish the Syrian government for an alleged chemical weapons attack.
Speaking in Paris, Secretary of State John Kerry said the number of countries ready to take military action is in the "double digits."
France has so far been the only country to publicly announce it could join Washington in a military operation.
Earlier, European Union foreign ministers blamed the Syrian government for the August 21 alleged chemical attack, and called for a “clear and strong response.”
But the statement did not explicitly back military action. It also said there should not be any response until United Nations weapons inspectors have reported the results of their probe.
French President Francois Hollande said he expected the UN report to be released within the next week.
Washington says the attack with sarin gas in Damascus suburbs killed more than 1,400 people.
The Syrian regime has denied carrying out the attack, instead accusing rebel forces of doing it in a bid to trigger Western military intervention in the conflict, which is now in its third year.
In his remarks, Kerry compared Syrian President Bashar al-Assad to Nazi dictator Adolf Hitler and Iraqi dictator Saddam Hussein, who were both responsible for unleashing chemical weapons.
"These are chemical weapons which, for almost 100 years, the world has banned from usage," Kerry said. "And in time of war, the only people who have used them are Adolf Hitler and Saddam Hussein, until Bashar al-Assad."
Kerry also warned that if action is not taken against the Syrian government, terrorists could obtain chemical arms and potentially use them against the West.
French Foreign Minister Laurent Fabius, who appeared with Kerry, said there was "wide and growing support" to take action against the Syrian government.
Fabius said that seven of the Group of Eight countries – excluding Russia – support a strong response to the Syrian government, along with 12 of the countries in the Group of 20 major economies.
Kerry’s visit to Europe came ahead of a week in which the prospect of strikes is expected to dominate debate in the U.S. congress.
President Barack Obama has asked lawmakers to approve a resolution authorizing the use of force, and a vote is expected this week.
But it remains unclear whether a resolution has enough support in Washington to pass.
Lawmakers who have expressed doubts about a strike have cited concerns about whether the United States could be drawn into a prolonged conflict, and whether such an operation will strengthen Islamic extremists who are fighting on the opposition side.
Reports have emerged saying U.S. officials had shown lawmakers gruesome videos of some of the victims of the alleged chemical attack, many of them children.
CNN has broadcast some of the videos, but said it could not confirm their authenticity. Supporters of the Syrian rebels had originally posted the videos on YouTube.
Obama is due to give a series of interviews and deliver a televised address on Syria on September 10 to press the case for strikes.
Based on reports from AFP, AP and Reuters