Secretary of State Cyrus R. Vance began his search for a path to Arab-Israeli peace here tonight in the belief that procedural barriers to a new Geneva conference may be overcome by June.

Vance on the first step of a six-country tour, by Israeli Foreign Minister Yigan Allon who told him, "It is high time that the political momentum should be revived . . . We should like to see movement in the area toward peace."

A briefing for American reporters by a senior Israeli Foreign Ministry official was in stark contrast to that optimism. Taking a very tough line on crucial and immediate issues, the official asserted that the way to a new Geneva conference is blocked by Arab demands that the Palestine Liberation Organization be represented.

"In its present form there is no way for the PLO to be part and parcel of the negotiating process - through the main door, the back door or the windows" the Israeli official declared.

The U.S. position on the PLO is complicated by a secret memorandum given to Israel in the fall of 1975 by Vance's predecessor, Henry A. Kissinger. It stated that Israel will have a veto over any new participants in a Geneva peace conference and pledged that the United States "will not recognize or negotiate with the PLO so long as the PLO does not recognize Israel's right to exist and does not accept Security Council resolutions 242 and 338."

The PLO is reported to be moving toward explicit recognition of Israel's existence but its "right to exist," which implies approval, is a greater problem. So is PLO acceptance of the U.N. resolutions, one of which refers to Palestinians simply as "refugees."

Before leaving Washington, a senior State Department official told reporters that Kissinger's pledges to Israel about the PLO and Geneva are binding on the Carter administration and can be changed only with Israel's approval. The Israeli Foreign Ministry official took the same position about the Kissinger memorandum, which was leaked to the press in September, 1975.

Israel takes the position that PLO recognition of Israel's right to exist can come only through major revisions of the organization's founding charter, similar to its constitution. The U.S. position on this point is not known. A Palestinian National Council meeting scheduled for March 12 in Cairo - the first such meeting of the movement's parliament-in-exile since June 1974 - is expected to consider changes in the charter.

As Vance set out on the whirlwind seven-day trip to six nations, his first foreign journey as Secretary of State and his first visit to any of the countries, informed sources said he plans to concentrate on the substance rather than procedures of an ultimate peace settlement. Vance is hoping for private signs of willingness by opposing parties to compromise their sharply conflicting official positions.

Vance has said repeatedly that it is of critical importance to obtain new progress toward Middle East peace this year. Despite the many hurdles to a resumption of the overall negotiations, reporters aboard his plane were told that he believes the procedural problems could be overcome in the first half of this year and after that, substantive negotiations should begin.

It was also learned that Vance plans to visit West Germany, France and England on the way home from a four-day visit to Moscow next month, and that he is considering a trip to China before the end of the year.

On his arrival here, Vance said it is fitting that his first diplomatic mission should begin with discussions between nations that are "old friends."

As his predecessors have done before him, the new Secretary of State reiterated that the United States is "deeply committed to the security and survival of Israel."