The Rev. Jesse Jackson, returning from a two-week tour of the Middle East, asked the Carter administration yesterday to abandon its policy against substantive contacts with the Palestine Liberation Organization.

After a 90-minute meeting with Ambassador Robert Strauss and Assistant Secretary of State Harold H. Saunders, the civil rights leader said his Number One recommendation was, "Let's talk to the PLO."

Jackson, head of Chicago-based Operation PUSH, said the leaders of Jordan, Lebanon and Syria, as well as Egyptian President Anwar Sadat, described the PLO to him as "the accepted organization of the Palestinian people" and the sole bargaining agent for Palestinians in peace negotiations.

"The PLO is not merely a terrorist gang, even though it has engaged in some terrorist acts," he said. "It is a government in exile."

Jackson said that Sadat, in a conversation with him last week, urged the United States to begin conversations with the PLO. He also quoted Sadat as saying that Egypt would accept an international conference to broaden the negotiations on an Arab-Israeli peace.

Israel refuses to have official contact with the PLO because of the organization's sponsorship of terrorist acts and its refusal to accept the existence of the Jewish state. The Carter administration is abiding by a U.S. pledge, which originated in 1975 with then-Secretary of State Henry A. Kissinger, not to recognize or negotiate with the PLO until it accepts Israel's right to exist.

During his trip Jackson met PLO Chairman Yasser Arafat but was denied a meeting with Israeli Prime Minister Menachem Begin and other top officials of his government. The civil rights leader said he regretted Begin's refusal to see him, because "a major shift has taken place" in the black community that is of importance to Israel.

"I'm convinced that peace is possible in the Middle East through a new formula for Israel's security and justice for the Palestinians," Jackson said. He did not elaborate on these generalized aims, which are rhetorically supported in the Middle East and the United States.

Jackson said he hopes to testify before Congress on his findings and to meet with American Jewish and American Arab leaders. He said he plans to articulate PLO positions to the nation but expects to devote most of his energy in the future to domestic civil rights work, rather than to Middle East affairs.