Israeli government officials were casting about yesterday for motives for what they termed an American overreaction to Israel's plans to expand Jewish settlements on the West Bank.

While professing bafflement over the intensity of President Carter's criticism contained in a message to Prime Minister Menachem Begin, these officials suggested two motives behind the indignation.

The feeling here is that the Americans are seeking to blunt in advance Israel's expected demands for substantive revision of the Egyptian-Israeli draft treaty that the Cabinet approved "in principal" Wednesday but to which it attached a string of amendments that have to be negotiated anew when the Washington talks resume.

The proposed revisions deal with the question of linkage between the bilateral Egyptian-Israeli treaty and future negotiations on Palestinian self-determination on the West Bank and Gaza Strip.

U. S. officials are known to be expecting and Israeli attempt to water down the preamble linkage, which Egyptian President Anwar Sadat wants as a way of demonstrating to his Arab critics that he has not abandoned the Palestinian Arabs.

The interpretation here is that by putting Israel on the defensive on the settlement issue, the United States will weaken Israel's bargaining position at the Blair House talks, and thereby improve the prospects for preserving the preamble as it stands.

The second motive that is widely assumed to be behind the U.S. reaction is a desire on Carter's part to prevent Sadat from overreacting to Begin's settlement announcement, which could lead to a collapse of the Camp David agreements.

The United States, it is felt here, coopted Sadat's indignation and gave the Egyptian president an alibi for not launching an attack on Begin.

"Washington had to react on behalf of Sadat. He says all the time that the United States is a full partner, in the talks, so the Americans are in a position to do his complaining for him," one Israeli official said last night.

Another official, Eliahu Ben-Ellisar, director general of the prime minister's office, expressed "astonishment" at the U.S. reaction and said the furor was "artifical and designed to serve a purpose," which he did not define.

Finance Minister Simcha Ehrlich pointed out that the U.S. knew about Israel's settlement expansion plans in advance, and said there is a "limit to provocation."

Several other informed Israeli officials offered similar interpretations of the U.S. reaction, and all of them expressed puzzlement of the intensity of it.

"The very strong criticism from the United States, in some part, is not understood here. It is out of proportion to what was announced" by Begin, said another Foreign Ministry official.

"The criticism itself may itself cause an obstacle to peace in Washington talks, because it may invite a reaction by the Egyptians," he added.

All of the Israeli officials interviewed traced the troubles back to the visit here last week by Harold Saunders, assistant secretary of state for Middle Eastern affairs, who aroused Begin's rightist critics in the Likud bloc by meeting with West Bank Arab leaders.

Saunders has not said what he told the Arabs at the closed meetings, but the perception of Israeli officials is that he encouraged them to believe that Israel will acquiese on its claim of sovereignty to the West Bank eventually, and emphasized that the United States does not agree with Israeli West Bank policy.

"There he is telling the United States doesn't agree with Israelis position on the West Bank and East Jerusalem, even before we begin negotiations," one Begin aide said, adding that the prime minister was infuriated by Saunders' visit.

The feeling among Israeli officials was that Saunders provided Begin with a ready-made excuse for announcing the settlement expansion, for which Likud rightists have been pressing for months.

"There never was a question of Israelis right [to expand settlements]. But the timing was in Saunders' hand," Finance Minister Ehrlich was quoted as saying.

Government officials, to some degree, and the Israeli press almost unanimously, have come to the conclusion that Saunders went beyond merely articulating known U.S. positions when he met the Arab leaders.

The newspaper Maariv, quoting an anonymous Arab leader, said Saunders left the West Bankers with the impression that they faced difficult times because of Israel's interpretation of the autonomy plan in the Camp David agreement, and that the United States would continue to resist that interpretation.

The newspaper Yediot Aharonot said Saunders moved into West Bank as a "high commissioner," and left and Arabs with the impression that Israel would give up its rights to the area.The "high commissioner" reference was a stinging reminder of British mandate rule over Palestine.

On the settlement controversy, the newspaper Davar published a statement it said Carter made at a Sept. 28 press conference, in which the president was quoted as saying that he agreed with the need to strengthen Jewish settlements.