WASHINGTON (CNN) -- Arguing that "the war is the most important issue confronting the American people," Sen. Arlen Specter, R-Pennsylvania, Tuesday called for hearings to investigate the scope of Congress' legal authority to alter President Bush's strategy in Iraq.

"The Congress cannot be pushed to the sidelines as the President commits more troops and ever-increasing funds to an engagement that commands uncertain support," Specter said in the letter addressed to Senate Judiciary Committee Chairman Patrick Leahy, D-Vermont. "We have an obligation to determine how, within appropriate constitutional constraints, we may engage the President and ensure that the will of the American people regarding this conflict is heard.

"To this end, it would be in the public interest for the Judiciary Committee to conduct a series of hearings to determine the constitutional authority of the Congress to limit conduct of the war," added Specter, who serves as the senior Republican on the Judiciary panel.

The seven page letter details relevant legislative precedents, relative court decisions, and opinions by constitutional experts.

Specter's letter comes as two senior Democratic aides tell CNN that Senate Democratic leaders have tentatively agreed to try to modify the 2002 resolution that authorized the president to invade Iraq. The Democrats would do so by working to pass a new resolution putting additional restrictions on military action in the country.