U.S. President Barack Obama will again make the case for military action in Syria when he speaks with key lawmakers.
Mr. Obama is scheduled to meet with prominent Senator John McCain at the White House Monday. McCain has long urged the president to take forceful action against Syria, possibly even removing Syrian President Bashar al-Assad from power.
But many U.S. lawmakers remain skeptical, questioning whether the military should be involved at all.
U.S. officials Sunday briefed some lawmakers on intelligence showing the Syrian military dropped poison gas on civilians outside Damascus last month, killing more than 1,000 people.
International support for military intervention in Syria, despite evidence of a possible chemical weapons attack, has been waning. But NATO Secretary General Anders Fogh Rasmussen said Monday something must be done.
Russia, a long-time Syrian ally, questioned Monday the credibility of U.S. evidence the Assad government used chemical weapons. Russian Foreign Minister Sergei Lavrov also cautioned that any military strike will only make it more difficult to find a political solution.
The Syrian government denies using chemical weapons and says the rebels have used poison gas against Syrian troops.