While McCain has pressed for a greater role for the U.S. military, other lawmakers have expressed reservations about American involvement in another conflict and fears that weapons sent to the rebels could fall into the hands of al-Qaida-linked groups.
Sen. Chris Murphy, D-Conn., a member of the Senate Foreign Relations Committee, condemned the Assad regime but expressed serious concerns about the United States being pulled into a proxy war.
"There are many actions that the United States can take to increase our humanitarian assistance to refugee populations and opposition groups short of injecting more weapons into the conflict," Murphy said. "I urge the president to exercise restraint and to consult closely with Congress before undertaking any course of action to commit American military resources to Syrian opposition forces."
House Speaker John Boehner, R-Ohio, also urged the White House to consult with Congress.
"It is long past time to bring the Assad regime's bloodshed in Syria to an end," he said through a spokesman, Brendan Buck. "As President Obama examines his options, it is our hope he will properly consult with Congress before taking any action."
Associated Press writers Lolita C. Baldor, Kimberly Dozier, Donna Cassata, Andrew Taylor in Washington and Edith M. Lederer at the United Nations contributed to this report.