Hagel declined to discuss any of those possibilities, saying only that he was providing options to the president.
The White House reiterated Monday that it did not yet know whether the "red line" Obama set on chemical weapons had been crossed.
White House press secretary Jay Carney said that a deadline would not be set for determining whether Assad’s forces used chemical weapons.
Carney has said that physiological tests found sarin gas had been used, but that the evidence needed to be verified before the president takes more aggressive steps. Obama said Friday that if chemical weapons were used, it would be a “game changer.”
The White House is urging Assad to cooperate with a United Nations investigation into possible chemical weapons use, although administration officials have said they are using other means to investigate as well.