McCain, the senior Republican on the Senate Armed Services Committee, said in a CBS interview possible steps include no-fly zones or safe corridors allowing them to get out of the country but said the United States should not send troops in.
"The United States should play a very important role ... along with other nations," McCain said. "Look, they're massacring their people."
McCain said the Arab League "has been very good on this" and is likely to be a good ally in the effort.
President Bashar Assad has stepped up the government assault on the city of Homs, the largest attack since he began cracking down on protesters last year.
Obama administration officials vowed Wednesday to gather "friends and allies who support the Syrian people," a promise echoed by Turkey.
"In the coming days we will continue our very active discussions with friends and allies who support the Syrian people, along with the opposition Syrian National Council, to crystallize the international community's next steps in that effort to halt the slaughter of the Syrian people and to pursue that transition to democracy," White House spokesman Jay Carney told reporters Wednesday.
State Department spokeswoman Victoria Nuland said the friends and allies would seek to tighten sanctions on the regime of President Bashar Assad and to get humanitarian aid to besieged Syrians.
Secretary of State Hillary Clinton initiated a "friends of a democratic Syria" theme Sunday -- a day after Russia and China vetoed a U.N. Security Council resolution pressing Assad to step aside -- when she said the Obama administration would now "work with the friends of a democratic Syria around the world to support the opposition's peaceful, political plans for change."
Two days later Turkish Prime Minister Recep Tayyip Erdogan said Ankara could not stay silent after the "fiasco" of the Russian and Chinese veto and vowed to "launch a new initiative with countries that stand by the Syrian people instead of the regime."
At the same time, senior European Union officials said Wednesday the 27-nation body would soon impose harsh new sanctions on Syria, The Wall Street Journal reported.
And the nine-member Gulf Cooperation Council and the 22-member Arab League planned to take action on Syria at separate meetings this weekend.
Six council members -- Bahrain, Kuwait, Oman, Qatar, Saudi Arabia and the United Arab Emirates -- withdrew their ambassadors from Damascus and expelled Syria's envoys Tuesday.
The league separately asked the United Nations to join it in sending observers back to Syria, U.N. Secretary-General Ban Ki-moon told reporters in New York Wednesday. The league's earlier mission was scrapped due to flagrant violence.
The Assad regime escalated its onslaught on the Syrian opposition Wednesday with the most intense bombardment on rebel-held areas so far, activists said.
As many as 60 people died in the western city of Homs near Lebanon as government forces bombarded Syria's third-biggest city for a sixth successive day, the Syrian Observatory for Human Rights opposition group in London said.