WASHINGTON — The goal of the cruise missile strikes the United States is planning to carry out in Syria is to restore the smudged “red line” that President Obama drew a year ago against the use of poison gas.

If carried out effectively, the strikes may also send a signal to Iran that the White House is prepared to back up its words, no small consideration for an administration that has proclaimed that the use of military force remains an option if the leadership in Iran insists on fielding a nuclear weapon.

But the military strategy that the Obama administration is considering is not linked to its larger diplomatic strategy of persuading President Bashar al-Assad of Syria to yield power and support negotiations that would end the bloody civil war.

Even if the American-led attack includes allied aircraft, the options that appear to be under consideration by Mr. Obama for Syria — one or two days of cruise missile strikes from at least four United States Navy Arleigh Burke-class destroyers in the Mediterranean Sea — would not amount to the sort of open-ended campaign that might compel Mr. Assad to negotiate a transfer to a transitional government.