WASHINGTON — Senator Rand Paul is calling for a declaration of war against the Islamic State, a move that promises to shake up the debate over the military campaign in Iraq and Syria as President Obama prepares to ask Congress to grant him formal authority to use force.

Mr. Paul, a likely presidential candidate who has emerged as one of the Republican Party’s most cautious voices on military intervention, offered a very circumscribed definition of war in his proposal, which he outlined in an interview on Saturday. He would, for instance, limit the duration of military action to one year and significantly restrict the use of ground forces.

Unlike other resolutions circulating on Capitol Hill that would give the president various degrees of authority to use force against Islamic militants, Mr. Paul would take the extra step of declaring war — something Congress has not done since World War II.

The president has said he will ask Congress for the explicit authority to fight the Islamic State, though administration officials have insisted that he has the legal power to continue the current campaign. That position has rankled many in Congress who are concerned that the White House has been waging war without the proper oversight or accountability.