Secretary of State George P. Shultz today turned down a Lebanese appeal that the United States take part in arranging withdrawal of Israeli military forces, saying "much more flexibility" and "quite a change in mood" on all sides would be required before such an effort would be undertaken.

The Lebanese request and Shultz's refusal came in a meeting of almost two hours with Prime Minister Rashid Karami and members of his "national unity" government, including Shiite leader Nabih Berri, minister in charge of Israeli-occupied southern Lebanon.

U.S. and Lebanese sources, reporting today's exchange, said further exploration and discussion is expected in next week's Washington meetings with Israeli Prime Minister Shimon Peres and in lower-level contacts with various parties by Assistant Secretary of State Richard W. Murphy.

Murphy returned last weekend from a nine-day Mideast journey and reported that protagonists in the latest chapter of the Lebanon drama are far apart.

Lebanon's appeals and its position in today's meeting, together with U.S. unwillingness to become involved, indicated that negotiated arrangements for an early Israeli withdrawal could be more difficult than generally anticipated. Lebanon has made it clear, according to participants in the meeting, that it is not willing to negotiate directly with Israel. Hence the request that the United States act as intermediary, which Shultz did early last year, fashioning a Lebanese-Israeli pact later repudiated by the government in Beirut.

Shultz and the Lebanese did not mention that moribund agreement in today's session, according to officials present. Despite diplomatic niceties, no one expressed doubt that this painful history plays a role in the U.S. position.

Another painful subject, terrorist acts that have cost American and Lebanese lives in repeated attacks on U.S. installations, was addressed by Shultz in "direct and forceful" fashion at the start of today's meeting, according to the U.S. account.

"Terrorism will not change U.S. policies and should not change the policies of other governments," Shultz was quoted as saying.

Karami's position, according to Lebanese sources, was that continued Israeli occupation and conflicts with Lebanese communities is a prime source of extremism that generates and encourages terrorism. This position implicitly shifts some of the blame for attacks on Americans to the Israeli occupation.

The most difficult security issue discussed today, and a central point in Shultz's appeal for flexibility, was the future of the Israeli-backed Lebanese force in southern Lebanon headed by Gen. Antoine Lahad, according to a participant.

Some or all of the elements of the new Israeli unity government are insisting on a continuing security role for Lahad's force of about 2,000 men after withdrawal of Israeli regulars.

Karami, who considers this force illegitimate, rejected such a role, the source said.

Instead, the Karami government said it has drawn up a security plan that contemplates assignment of about 9,000 Lebanese Army troops and the 5,700-man U.N. peace-keeping force, UNIFIL, to ensure security in southern Lebanon after Israeli withdrawal.

Lebanese officials argued that even a modest force could readily control the large area of southern Lebanon if the troops were welcomed and assisted by a friendly local population.

On the other hand, they said, even heavily armed troops, such as the Israelis, will have constant trouble if not accepted by the populace.