Secretary of State Cyrus R. Vance, in two meetings with American Jewish leaders and journalists within 48 hours, attempted to quell suspicions that the Carter administration is undercuting Israel in its drive for Arab-Israeli peace talks.

After the meetings with Vance yesterday and Wednesday, participants expressed appreciation for the encounters, but indicated their concerns and disquiet were not dissolved.

Israeli apprehensions about Carter administration policy came close to being intensified yesterday. In a U.N. General Assembly vote to censure Israel for establishing Jewish settlements in establishing Jewish settlements in occupied Arab territories, the United States decied to abstain after failing to get a change in the condemnatory resolution.

Only Israel voted against the resolution, which declares that the Jewish settlements "have no legal validity and constitute a serious obstruction" to peace negotiations.

The United States has expressed the same position, but it balked at the U.N. resolution primarily because it reffered to "Palestinian and other Arab territories."

Use of the "Palestinian" terminology, administration officials said, implied an endorsement of a Palestinain state, prejudging a central issue that would be in the Geneva conference on the Middle East, which the Carter administration seeks to convene in December.

Administration officials said the United States told the resolution's sponsors that if the "Palestinian" reference was deleted, the United States could support it. The Arabs and other sponsors caucused yesterday and declined to make the change.

Vance assured 51 editors and reporters from American Jewish publications in a background talk yesterday that there is no way that the Palestinian Liberation Organization can be brought into a Geneva conference as long as Israel refuses to accept it as a bargaining partner.

Alfred L. Atherton Jr., assistant secretary for the Middle East, and Vance faced skeptical questions nevertheless about U.S. intentions, participants said.

On Wednesday, Vance had an angrier audience in an off-the-record talk to 76 American Jewish leaders. Rabbi Alexander M. Schindler, chairman of the Conference of Presidents of Major American Jewish Organizations, said after: "The Jewish community expresed its concern, its frustrations, its anger."

Vance told both audiences that the administration has no intention of reneging on its commitments to support Israel's security, or to reduce the level of American military or economic aid to Israel.

For the next fiscal year the State Department has recommended for Israel the same amount of aid, $1.8 billion, as last fiscal year, the largest amount for any foreign aid recipient. As now proposed, $1 billion again would be in military credits, only half of which israel would repay, plus $800 million in economic grants and loans.

However, American-Jewish apprehensions continue about the administration's diplomatic intentions. Sen. Jacob K. Javits (R-N.Y.), speaking in Denver last Sunday about "substantive differences between Israel and the Carter administration," said: "There could be a crunch coming in U.S.-Israeli relations relative to the Geneva conference, and I believe that Americans deeply interested in Israel should be prepared for the very exacting role they may be called upon to play should this happen."

Some of these concerns will be aired in the international conference of the General Council of the World Jewish Congress, which opens Sunday evening at the Capitol Hilton hotel.

Speakers include President Carter, Wednesday evening; Andrew Young U.S. ambassador to the United Nations, who is to speak at a Monday luncheon: Senate Republican leader Howard H. Baker Jr. (Tenn.), to speak at a luncheon the next day, and former Secretary of State Henry A. kissinger, who is to address the delegates Thursday.