The new classified policy guidance imposes tougher standards for when drone strikes can be authorized, limiting them to targets who pose “a continuing, imminent threat to Americans” and cannot feasibly be captured, according to government officials. The guidance also begins a process of phasing the C.I.A. out of the drone war and shifting operations to the Pentagon.

The guidance expresses the principle that the military should be in the lead and responsible for taking direct action even outside traditional war zones like Afghanistan, officials said. But Pakistan, where the C.I.A. has waged a robust campaign of air assaults on terrorism suspects in the tribal areas, will be grandfathered in for a transition period and remain under C.I.A. control.

That exception will be reviewed every six months as the government decides whether Al Qaeda has been neutralized enough in Pakistan and whether troops in Afghanistan can be protected. Officials said they anticipated that the eventual transfer of the C.I.A. drone program in Pakistan to the military would probably coincide with the withdrawal of combat units from Afghanistan at the end of 2014.

Even as he envisions scaling back the targeted killing, Mr. Obama embraced ideas to limit his own authority. He expressed openness to the idea of a secret court to oversee drone strikes, much like the intelligence court that authorizes secret wiretaps, or instead perhaps some sort of independent body within the executive branch. He did not outline a specific proposal, leaving it to Congress to consider something along those lines.

He also called on Congress to “refine and ultimately repeal” the authorization of force it passed in the aftermath of Sept. 11. Aides said he wanted it limited more clearly to combating Al Qaeda and affiliated groups so it could not be used to justify action against other terrorist or extremist organizations.

In renewing his vow to close the Guantánamo prison, Mr. Obama highlighted one of his most prominent unkept promises from the 2008 presidential campaign. He came into office vowing to shutter the prison, which has become a symbol around the world of American excesses, within a year, but Congress moved to block him, and then he largely dropped the effort.

With 166 detainees still at the prison, Mr. Obama said he would reduce the population even without action by Congress. About half of the detainees have been cleared for return to their home countries, mostly Yemen. Mr. Obama said he was lifting a moratorium he imposed on sending detainees to Yemen, where a new president has inspired more faith in the White House that he would not allow recidivism.