Secretary of State Cyrus Vance, spearheading a growing U.S. effort to advance the Camp David accords, appealed to the Palestinian people yesterday to "seize this historic opportunity" to win a place in a peaceful Middle East.

In the annual U.S. policy address to the United Nations General Assembly, Vance sought to counter objections from Palestinians and many Arab governments, and to head off a political drive by an anti-Israeli majority in the U.N. to oppose the Camp David agreements.

Vance emphasized his view that Camp David resulted in "a frameworkd for a comprehensive peace settlement" and "a dynamic process . . . that can profoundly change attitudes on the issues on the issues that remain to be resolved."

He called on the people of the Middle East "to begin the negotiating process now - and not to stand still until every last issue is revolved." He urged "other interested parties," apparently referring particularly to Jordon, to join the Egyptian-Israeli negotiations without delay.

Several hours after Vance spoke, Assistant Secretary of State Harold H. Saunders and other U.S. officials met Arab delegates in a U.N. conference room in an attempt to win support for the Camp David agreements. Similar meetings had been held previously for African and some European delegates. Other efforts in the same cause include a series of luncheons and dinners here given by Vance and Under Secretary of State David Newsom.

In the Middle East, U.S. roving ambassador Alfred Atherton planned a meeting with Palestinians living on the occupied West Bank and Gaza Strip to enlist their cooperation. The Camp David agreements gove crucial negotiatings and administrative role to a self-governing council to be made-up of Arab inhabitants of the occupied zones.

Senior U.S. officials have reiterated in recent days that the United States will continue to observe its self-imposed ban on recognizing or negotiating with the Palestine Liberation Organization (PLO) so long as that organization does not explicitly recognize Israel's right to exist. The United States agreed in writing to this restriction in the context of a future Geneva conference as part of the price of Israeli support for the September 1975 Sinai disengagement agreement.

However, a State Department official who briefed reporters on Vance's speech did not rule out dealings with the PLO in efforts to find an international solution to the Lebanese conflict. The official said "We've thought of the problem" but that no decisions have been made. He recalled that the United States did have contacts with the PLO about the security situation in Lebanon when American citizens were endangered there two years ago.

In his address, Vance repeated President Carter's call for a conference that might write a new charter for strife-torn Lebanon. But the official briefer cautioned that this initiative is "only in its infant stages," and there were indications that Carter's public announcement caught American diplomats by suprise.

Vance made no mention of the Camp David provisions calling for U.N. peacekeeping forces and observers in the Sinai as part of future arrangements there. Any expansion of the U.N. role there would have to be submitted to the Security Council, where the Soviet Union has a veto.

The diplomatic efforts of American officials and the tenor and emphasis in Vance's address arise in part from concern that the United Nations could become and impediment to the Camp David accords if the policy line of militant Arabs holds sway, as it often has there in hte recent past. These Arabs are bitterly critical of the failure of American and Egyptian efforts, in drawing up the guidelines for a Middle East peace, to obtain Israel's commitment to withdraw eventually from the West Bank and Gaza Strip.

Vance's speech was intended originally to dwell mostly on economic policies of importance to the developing nations, which make up a heavy majority of the 150-sear world assembly. While most of the 45-minute address concerned North-South maters, the major section on the Camp David agreements was the center of interest.

The U.N. audience, which did not interrupt with applause at any point and gave only polite applause at the end, was told that "all nations must enter international economic negotiations with a spirit of accommocation." Vance mentioned several U.S. decisions billed as moves in that direction.

Among the measures of compromise was change in the U.S. position on certain aspects of the proposed "common fund" to support basic commodity prices, shifting from opposition to a commitment to "negotiate flexibly."

Vance sounded alarm bells on the world food situation, saying that recent good harvests should not be allowed to conceal underlying problems. He called for a renewed sense of urgency about feeding the worlds fast-growing population and said that "another tragedy is inevitable unless we act now."