The White House on Monday said an additional 14 nations had signed up to a list of countries supporting a "strong international response" to what it says is Syria's use of chemical weapons.
The statement was put together at the G20 summit in Russia last week, and originally included 10 nations plus the United States.
On Monday, the White House says 14 more states, including Germany, Qatar, the United Arab Emirates, Morocco and Kosovo had added their names to the statement.
"The statement explicitly supports the efforts undertaken by the United States and other countries to reinforce the prohibition on the use of chemical weapons," the White House said.
However, the document does not make any explicit mention of the use of military force, which US President Barack Obama has threatened against the Assad regime.
"We call for a strong international response to this grave violation of the world's rules and conscience that will send a clear message that this kind of atrocity can never be repeated," the statement reads.
"Those who perpetrated these crimes must be held accountable."
Other nations revealed as signing the document on Monday were Albania, Croatia, Denmark, Estonia, Honduras, Hungary, Latvia, Lithuania and Romania.