The United States and Israel took opposing stands yesterday on including Palestinians in a unified Arab delegation at a Geneva peace conference.

A "single Arab delegation deserves serious consideration as a way of resolving issues that have arisen concerning participation in a Geneva conference," a State Department spokesman said.

Although the spokesman added that "there are, of course, other options," Carter administration sources made it clear that they regard the single, unified Arab delegation as the likeliest formula for Arab-Israeli peace talks. American officials stressed that to be included in the Arab grouping the Palestinians would have to accept a United Nations resolution acknowledging Israel's right to exist.

Israel brushed aside a similar formula during Secretary of State Cyrus R. Vance's round of Arab-Israeli shuttle diplomacy last month. But the Carter administration, nevertheless, has concluded the plan raises "the least resistance on the Arab side," as one source put it, and will seek to convince Israel that it can be refined in a manner to protect Israel's vital interests.

The United States and Israel "do not agree with each other" on Palestinians joining the peace talks, Israeli Foreign Minister Moshe Dayan said yesterday, en route to talks in Washington on Monday.

Dayan, leaving Tel Aviv for a stop-over in Brussels , said Israel would accept only nonmembers of the Palestinian Liberation Organization as part of a Jordanian delegation in peace talks and Israel would reject any negotiations with the PLO, which it calls "a terrorist" organization.

He was commenting primarily on the Carter administration's earlier move this week in setting the stage for talks with Dayan and Arab foreign minister in Washington and New York during the next two weeks.

Monday the State Department said that "the Palestinians must be involved in the peacemaking process. Their representatives will have to be at Geneva for the Palestinian question to be solved."

Dayan said, however, "We are willing to sit down with the Palestinians of the West Bank (of the Jordon River) and the Gaza strip but not at the Geneva conference, which is intended for states to reach peace treaties."

He also said "We do not think the Palestinians should be at Geneva on their own or on equal terms with other Arab delegations."

The challenging task the Carter administration faces is to induce the Arab nations - Egypt, Syria, Saudi Arabia, notably, and Jordan - to convince the PLO to agree to allow other Palestinians to join a single Arab delegation. The Carter administration then must convince Israel that the Palestinians selected are not PLO officials and that there should be a unified Arab delegation.

Israeli Prime Minister Menahem Begin said in Washington in July that Israel is "not going to search the pockets" of "Palestinian Arbs" in a Jordanian delegation "to look for credentials." But he said no "man of the so-called PLO" would be accepted.

On another Arab-Israeli issue, State Department spokesman Kenneth L. Brown said yesterday that the United States favors an impartial international investigation of charges that States favors an impartial cinternational investigation of charges that Arabs in the occupied West Bank have been subjected to systematic torture in Isracli jails.

The Swiss Human Rights League has accused Israel of violating the Universal Declaration of Human Rights. Israel has denied the charges, and Brown asaid an inquiry would help to resolve the accusations.

A spokesman for Israel's prime minister said yesterday that Begin assured Carter in July that the charges are unfounded, and to allay concern, Begin issued new orders to security and prison officials. The spokesman called the torture charges "vicious slanders."