After a long day of listening to Israel's unchanged position on the search for peace in the Middle East, Secretary of State Cyrus R. Vance said tonight he is still aiming for the convening of a new Geneva conference in the second half of this year.

Vance made little public comment and, according to officials, little comment in the private talks on the substance of Israel's position, most of which is widely known.

The fact that he continued to express optimism about the start of a new peace effort, despite thorny problems raised by Israel's views, was taken as a sign of U.S. determination to move ahead.

Vance said he found some "flexibility" here on the part of Israeli officials, but an Israeli spokesman said there was "nothing new" in the substantive declarations. Prime Minister Yitzhak Rabin said publicly and in meetings with Vance that Israel will attend a new Geneva conference with Arab states only on its terms, which exclude participation by the Palestine Liberation Organization.

Vance seemed to hint at a slight stiffening of the U.S. position on the PLO, saying the Palestinians should nto participate at Geneva "as long as they stand by the convenant" calling Israel illegal and refuse to accept U.N. Security Council resolutions 242 and 338.

Previously Vance had linked the U.S. attitudes toward the PLO to that organization's recognition of Israel's "right to exist" and of the U.N. resolutions, without mention of its conventant. The covenant, which is the PLO's governing charter, may be revised at a meeting of the Palestinian National Council scheduled for March 12 in Cairo.

Rabin, who is in the final week of a hotly contested race with Defense Minister Shimon Peres for his party's leadership, was invited to visit Washington early next month to confer with President Carter. Perres said he did not object to the trip, since Rabin will be in office at that time no matter who wins next week's Labor Party balloting.

Vance said he hopes that leaders of the five Arab states he will visit begiinning with Egypt Thursday, will come to Washington in March and April to see Carter about peace talks in today's meetings Vance did not pro.

Israeli officials told reporters that pose new ideas about the Middle East peace process. He was depicted as an attentive listener who occasionally asked clarifying questions.

In a toast at an official dinner, Foreign Minister Yigal Allon quoted from a statement made by Carter during the U.S. presidential campaign endorsing Israel's requirement for "defensible borders" and saying that the U.S. should never attempt to impose a peace settlement on Israel.

"Only an American policy based on these essential principles will conduce to peace," Allon declared.

Vance said tonight and Allon agreed that it may be usefull to have "a preliminary conference" before the convening of several countries in Geneva-style peace negotiations. No details of a preliminary session were given.

Today's talks included discussion of the recent U.S. decision to black Israel's proposed sale of high-performance Kfir fighter planes, which U.S. engines, to Ecuador. Washington's reassessment of former President Ford's decision to sell "concussion bombs" too Israel was also discussed.

Israeli officials appear to be more upset about losing the sale of fighters than about the possibility of not being permitted to purchase the powerful bombs Israel fears that its budding arms industry will be set back by the U.S. decision restricting it from exporting weapons with U.S. components to various countries including South Africa and Latin American states.

Vance was asked by Israeli officials to broach with Lebanon and Syria the idea of a permanent arrangement to defuse tension in southern Lebanon arising from Syrian troop deployment near the Israeli border.

The United States acted as intermendiary recently in helping to arrange the withdrawal of Syrian troops from the border area after threats of military action by Israel.

Peres asked Vance to discuss with the Arabs mutural measures against the surprise attacks between Israel and its neighbors, sources aid.

ments at the start of his Middle East tour "left no room for optimism."

Al Baath said Vance's expressed priorities - a peace settlement first then Israeli withdrawal from occupied territory and finally a solution to the Palestinian problem - were the reverse of what "logic" demanded

Syrian President Hafez Assad, ending a two-dy visit to Romania, accused Israel of a "rigid" stance that prevents progress toward peace but he made no criticism of Vance, with whom he is to meet Sunday.

Meanwhile, French Foreign Minister Louis de Guiringaud arrived in Beirut at the start of a Middle East tour aimed at finding what France can do to help settle the Middle East conflict.