Congressional leaders, in dealing with the Iraq crisis, are looking to regain a constitutional role that was lost 40 years ago when President Harry S. Truman dispatched troops to Korea without first asking Congress for a declaration of war.

But as House Speaker Thomas S. Foley (D-Wash.) and Senate Majority Leader George J. Mitchell (D-Maine) have discovered, getting President Bush to seek or wait for congressional action may prove less of a problem than getting some of their colleagues to permit a straightforward, up-or-down vote on the use of force against Iraq.

"This is not the same place where {House Speaker Sam} Rayburn and {Senate Majority Leader Lyndon B.} Johnson could order up votes," said one legislator after Foley and Mitchell yesterday revised their timetable for debating resolutions in order to meet objections of members who oppose any use of force in the Persian Gulf crisis.

"The Congress can no longer be used as a positive instrument," he said.

Mitchell and Foley frequently have reminded Bush in their meetings that they want congressional action to enhance his credibility with Iraq's President Saddam Hussein and not detract from it. But, as Mitchell said Thursday, "It does us no good to sacrifice our constitutional principles to achieve {that} objective."

If the 400,000 U.S. troops being assembled in the gulf are used in an unprovoked offensive action to free Kuwait without prior congressional authorization, it will be a war and the leaderships' argument that it must authorize such an action "will be moot," as one top Senate aide put it.

As with the Persian Gulf conflict, U.N. resolutions in June 1950 set a framework for U.S. entry into the Korean War. Truman ordered U.S. air and naval forces to help defend South Korea two days after the United Nations demanded that North Korea halt its invasion. The war, the first in which the United Nations played a military role, ended in July 1953, although a permanent peace treaty between the two nations has never been signed. More than 54,000 Americans died in the war, with a financial cost to the United States of almost $67 billion.

Although Foley and Mitchell plan to await the outcome of the latest round of gulf diplomacy before moving on any legislation, they apparently have concluded that a time could come when Congress has to support the president and authorize his use of force as an option.

"The substantive disagreement is whether the resort to force should be early, or whether the resort to force should be a truly last resort, only after all other means have been exhausted," Mitchell said Thursday after meeting with Bush.

As Foley framed it, "The question of a debate and action on some resolutions regarding affirmative force, or offensive force, is one that will have to be taken at some appropriate time."

White House press secretary Marlin Fitzwater, after noting that the congressional leaders agreed that force was an option that the president should have, described the difference as one of "the timing."

"Do you go in on the 14th {of January} or the 15th or the 21st," Fitzwater said, "or do you wait six months or 12 months or 18 months, and that's where the debate lies. And that's a legitimate debate."

After their meeting with Bush, Mitchell and Foley acted as if they believed Bush would either go to Congress for a resolution supporting the use of force before the Jan. 15 deadline, or hold off any order for an attack until late January, giving Congress a chance to debate a resolution after Jan. 23. That was the date Mitchell initially planned to take up such legislation.

However, House members and senators who strongly oppose any use of force in the gulf area, led by Rep. Ronald V. Dellums (D-Calif.) and Sens. Brock Adams (D-Wash.) and Tom Harkin (D-Iowa), upset that schedule.

Because of their mistrust of Bush and fear he was prepared to go to war immediately after the Jan. 15 deadline, they wanted Congress to immediately begin debating a resolution that declared the president had to have congressional authorization prior to any offensive use of U.S. forces.

One Senate aide analyzed such a resolution's effect in this way: "Raising the constitutional issue provides an easy vote for Democrats and a hard one for Republicans."

Foley, however, warned a group of liberal House members who raised the issue with him Thursday evening that because it could be interpreted as a vote against the president's position, such a resolution stood a good chance of losing because of solid GOP opposition bolstered with votes from conservative and some moderate Democrats.

Rep. David R. Obey (D-Wis.), a strong critic of the use of force in the short term, said he opposed such a resolution because "it confuses issues," and said when Congress votes it ought to be directly on the issue of using force.

Rep. Dante B. Fascell (D-Fla.), chairman of the Foreign Affairs Committee and a strong supporter of the need to reestablish a congressional role in matters like the gulf crisis, said no one knows what will happen in coming weeks in the Persian Gulf. The road to any Persian Gulf legislation is "fraught with dangers," he said, adding, "From a practical standpoint, I can't see it happening."