WASHINGTON — The apparent ease with which Israel struck missile sites and, by Syrian accounts, a major military research center near Damascus in recent days has stoked debate in Washington about whether American-led airstrikes are the logical next step to cripple President Bashar al-Assad’s ability to counter the rebel forces or use chemical weapons.

That option was already being debated in secret by the United States, Britain and France in the days leading to the Israeli strikes, according to American and foreign officials involved in the discussions. On Sunday, Senator John McCain, who has long advocated a much deeper American role in the Syrian civil war, argued that the Israeli attacks, at least one of which appears to have been launched from outside Syrian airspace, weakens the argument that Syria’s air defense system would be a major challenge.

“The Israelis seem to be able to penetrate it fairly easily,” Mr. McCain said on “Fox News Sunday.” He went on to say that the United States would be capable of disabling the Syrian air defenses on the ground “with cruise missiles, cratering their runways, where all of these supplies, by the way, from Iran and Russia are coming in by air.” Patriot missile batteries already installed in Turkey, he argued, could defend a safe zone to protect rebels and refugees.

The Pentagon developed such options months ago, but in recent weeks, the Joint Chiefs of Staff and Central Command, which runs military operations in the Middle East, have been asked to refine them and explore how strikes would be coordinated with allies, much as they were in the opening days of the attacks on Libya that ultimately drove Col. Muammar el-Qaddafi from power, according to several senior administration officials.