The crisis in the Persian Gulf has thrown into a federal court here a constitutional issue left unresolved since the Vietnam era: When does the president have the right to send troops to fight without congressional consent?

"If ever there was a case for judicial review of the {Constitution's} war powers clause, this is it," attorney Jules Lobel of the Center for Constitutional Rights told U.S. District Judge Harold H. Greene yesterday. Lobel represents 54 House members who raised the issue amid the most massive U.S. military buildup since Vietnam, challenging President Bush's right to deploy troops in the Persian Gulf on his own.

Two congressional committees opened hearings on the gulf situation. Former defense secretary Robert S. McNamara, who presided over the Vietnam buildup, told the Senate Foreign Relations Committee that the administration should give sanctions imposed against Iraq a year or more to work before going to war.

Across the Hill, House Armed Services Committee Chairman Les Aspin (D-Wis.) opened his hearings by saying, "The country is united on ends but divided on means."

At the same time, House Democrats overwhelmingly approved a non-binding resolution insisting that Congress give "affirmative approval" before the United States initiates offensive military action in the Persian Gulf.

Approved 177 to 37 in the Democratic caucus, the resolution is an expression of the desires of the caucus and has no practical effect. However, it indicates the strength of sentiment in Congress.

The lawmakers' suit, filed Nov. 20, seeks an injunction barring Bush from attacking Iraq without the congressional declaration of war provided for in Article I Section 8 of the Constitution.

If the right to "declare war" does not apply in these circumstances, Lobel asked the judge rhetorically, when would it apply? "Do we need a nuclear war?" he asked.

Greene echoed reservations of other federal judges in several cases since the mid-1960s, all unsuccessful challenges to presidential powers as commander in chief.

The issue, he said, can be viewed as a political clash between the legislative and executive branches, one that "doesn't have to involve the judiciary." He told Lobel, "No court has ever issued an injunction you are asking for."

Lawyers for the Justice Department told Greene that if he granted the congressmen's request, he would have to distinguish between actions such as the 1986 U.S. bombing raid on Libya and actual war. "The question before this court is, can this court define what a war is?" asked Stuart M. Gerson, assistant attorney general for the Civil Division.

"Mr. Lobel says there are 400,000 troops over there ready to march," Greene replied. "If that isn't war, what is?"

Gerson said the troops were there to provide Bush with military options. Congress's power to declare war, he argued, simply is the maximum U.S. declaration of hostility.

Besides, Gerson added, "nothing in the Constitution says when this declaration has to take place," whether before or after an attack.

Some of Greene's questions indicated he was troubled by an issue other courts have cited in declining to hear such cases at all, the legal doctrine that judges cannot issue advisory opinions on still-developing constitutional confrontations.

"There are discussions and negotiations going on with Iraq," Greene said, referring to Bush's proposal last week that he meet with Iraqi Foreign Minister Tariq Aziz and that Secretary of State James A. Baker III meet with Iraq President Saddam Hussein. He also noted last Thursday's United Nations resolution approving the use of force against Iraq if Saddam does not withdraw his troops from Kuwait by Jan. 15.

"So," the judge asked, "is this matter ripe for a decision?"

"Time is short," Lobel replied. "We are talking about the threat of war in six weeks." If Bush acts, Lobel added, he will do it quickly, "before the plaintiffs can come back into this court."

Lobel said Bush's statements that he has authority to order troops to fight without Congress's approval means he is ignoring the American people's views.

"I think the president is simply snubbing his nose at Congress, and I think the court should say he cannot continue to do so," Lobel said.

Staff writer Tom Kenworthy contributed to this report.