President Reagan yesterday told congressional leaders that conditions he has imposed on sending U.S. peace-keeping troops to Lebanon have not been met so far, and he assured them he would not take such a step without full congressional consultation.

In a White House briefing intended to assuage mounting concern on Capitol Hill about U.S. participation in a peace-keeping force, Reagan also told the bipartisan group that if troops are dispatched, it would be for "a very short action, a matter of a few days . . . not more than 30," according to Sen. Charles Percy (R-Ill.), chairman of the Foreign Relations Committee.

Percy and the others who attended the hour-long session emerged applauding Reagan for his commitment to abide by the War Powers Act of 1973, which requires a president to notify Congress within 48 hours after sending any American troops into a combat zone and which urges him to consult "in every possible instance" prior to doing so.

They also said they were reassured by his expressed determination to proceed with extreme caution.

"There is no one who will be more cautious than President Reagan in his commitment of forces," said Percy. "He knows the risks involved . . . but he also knows the risks of not acting."

When he said last week he had agreed "in principle" to sending troops to Lebanon to assure safe passage of trapped Palestine Liberation Organization forces out of Beirut, Reagan set forth these conditions:

* That the United States be officially asked by Lebanon to provide such a force.

* That all parties to the hostilities agree to any arrangement.

* That there be guarantees of the safety of the forces.

Percy said yesterday that Reagan had told them that the conditions had not been met, and House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) added, "I think we're far from an agreement."

While the meeting may have calmed fears on Capitol Hill of an imminent or surprise dispatch of forces, it did not produce any pledges from Reagan on the sticky question of whether he would make a report under the War Powers Act in a way that would skirt a 60-day time limit on the deployment.

The better known provision of the act--Section 4 (a) (1) calls for a president to report to Congress when U.S. forces are introduced "into hostilities or into situations where imminent involvement in hostilities is clearly indicated by the circumstances."

A report under that section commits the president to withdraw the troops within 60 days unless Congress declares war or adopts some other measure extending the time, or unless the president certifies that "unavoidable military necessity" requires an extension for not more than another 30 days.

However, the next section, 4 (a) (2), calls for the president to report to Congress whenever U.S. forces go "into the territory, airspace or waters of a foreign nation, while equipped for combat . . . . "

This section gives the president flexibility to use U.S. troops in situations that he deems not to be dangerous, without imposing a time limit on him.

Deputy White House press secretary Larry Speakes said that while Reagan had pledged to use the act, he was still uncertain which section he would use.

Critics of the proposal to send forces to Lebanon, led by Senate Majority Leader Howard H. Baker Jr. (R-Tenn), have objected to any role beyond an escort service for the PLO.

When Reagan first announced last week that some 1,000 Marines might go into Lebanon, he broached the possiblity that, in addition to guaranteeing safe passage, the troops might also "assist in the transition of authority to the Lebanese government in Beirut."

In yesterday's meeting with the 15 Congressional leaders, however, he reportedly stressed the short-term nature of any deployment.

Rep. Clement J. Zablocki (D-Wis.), chairman of the House Foreign Affairs Committee, said in a letter to the president last week that any skirting of the time provisions "could only be intrepreted as an attempt to avoid capriciously" the intent of the act.

Following the meeting, Zablocki said that Reagan had given assurances he would follow "not only the spirit but the letter of the War Powers Act." Then he added, incongruously, that there was still "some disagreement" as to which article to invoke.

In the briefing yesterday, the congressional group also heard a report from Peter McPherson, director of the Agency for International Development, who said urgent humanitarian aid was getting through to Beirut but that the longer-term need will be to provide economic assistance to rebuild the city.

Reagan also used the briefing to put in a plug for his Caribbean Basin Initiative, a package of economic and military aid he launched with some fanfare earlier this year and which has been stalled on the Hill.