WASHINGTON — The Obama administration vowed Wednesday to keep up the pressure on Syrian President Bashar al-Assad regime's, a day after China and Russia vetoed a UN Security Council resolution against it.

"The US will continue to work with as many countries as we can to increase the pressure on the Syrian regime," State Department spokeswoman Victoria Nuland told reporters.

"We do believe that despite this vote yesterday, the number of countries that is prepared to tighten the noose on the regime continues to grow and will grow and we will work with them," she said.

Russia and China vetoed a Security Council resolution late Tuesday which would have threatened possible measures against Assad's government.

Nuland said: "We firmly believe that history will bear out which nations were right and which were on the wrong side in this vote yesterday."

While Western nations expressed anger at the veto, Russia and China said any hint of sanctions is unacceptable.

Susan Rice, the US ambassador to the United States, said the United States was "outraged" at the Security Council's failure to take action against Syria.

In a similar vein, Nuland said Syrian opposition websites and blogs are expressing "enormous outrage and anger and disappointment, particularly directed at the vetoing countries.

"Clearly the brave and largely peaceful Syrian opposition that has been standing up to abuse and bullets and torture and arrests day after day in cities across Syria has been severely let down by this vote," she said.