The White House yesterday suggested that congressional Democrats' efforts to put some time limit on the deployment of U.S. Marines in Lebanon may be endangering the troops there.

Senate Democrats who have been arguing with President Reagan over his legal authority to deploy the troops without congressional authorization blasted back angrily.

"To suggest . . . that congressional insistence that the law be lived up to is somehow giving aid and comfort to the enemy is totally unacceptable," said Sen. Thomas F. Eagleton (D-Mo.).

A White House official, speaking on the condition that he not be identified, had said that "The Syrians are watching everything we do here, including our discussions with Congress. They are mindful of any restrictions on the Marines."

Four Marines in the multinational peace-keeping force in Beirut have been killed by artillery shells. There are reports, especially from the Lebanese government, that the Syrian army is heavily involved in the Beirut fighting.

The White House official said that any time limits Congress might impose on the Marines' deployment would offer the Syrians a timetable telling them when it was safe to step up the shooting.

"The administration has thrown out a red herring," Eagleton said, with "an attempt to intimidate the Congress and frighten the American people with this kind of ludicrous argument."

While they were exchanging these public barbs, the administration and the Senate Democrats met privately again yesterday at the Capitol to try to resolve their dispute over the application of the War Powers Resolution, a 1973 law that sets limits on deployment of troops overseas, to the Marines in Lebanon.

The negotiations again proved futile.

The Democrats complained that there was "no movement" in the White House position. For the Republicans, Senate Majority Leader Howard H. Baker Jr. (R-Tenn.) complained, in a statement from his spokesman, Thomas Griscom, that "there was no flexibility on the part of the Democrats."

The controversy involves a conflict between the president's constitutional powers as commander in chief of the armed forces, and Congress' constitutional authority to declare, or not declare, war.

The War Powers Resolution, passed at the end of the Vietnam war, which went on for eight years with no declaration of war, was designed to give Congress some control over extended overseas deployments of U.S. troops.

The Marine force in Lebanon, on duty now for about a year, is the first deployment since Vietnam long enough to bring the war powers law into question.

Congressional Democrats insist that the law requires Reagan to invoke a provision that would force him to bring the troops home within 60 days unless Congress authorizes a longer stay.

Reagan, wary of a precedent that might limit his military sway, has declined to invoke the law and has asked Congress for unconditional authority to keep the Marines on station.

Eagleton said early yesterday that the two sides were at an impasse. When the anonymous White House comment implying danger for the Marines was reported on Capitol Hill, Democratic leaders were infuriated and, if anything, hardened their position.

More negotiations are set for next week. In addition, the dispute will come before the Senate officially when two competing resolutions are brought forward.

The Democratic resolution demands that Reagan invoke the section of the War Powers Resolution that would put a 60-day limit on the deployment unless Congress authorized more time.

Baker announced last night that he will introduce a competing Republican resolution that, according to his press secretary, will refer to the War Powers Resolution. Precisely what it will say on the point has not been determined, but Baker reportedly will try to find language that strikes a compromise between his fellow Republicans in the White House and his Democratic colleagues in the Senate.

House Democrats, too, will be working toward a resolution asserting congressional authority over the Marines' deployment.

In his news briefing yesterday, White House press secretary Larry Speakes said that the situation in Lebanon has reached a "pivotal point."

He said the administration would "actively seek a resolution" to the constitutional controversy, but added that "our first interest is the safety of the U.S. Marines and their critical role in Lebanon."