Secretary of State George P. Shultz reopened talks Monday with Prime Minister Yitzhak Shamir, pledging the United States would oppose a Palestinian state and efforts to force Israel back to its pre-1967 borders.

The two-hour meeting at Shamir's office launched Shultz's second shuttle visit to the Middle East in a month and a new attempt to hold Arab-Israeli negotiations May 1 to provide some self-rule for Palestinian Arabs.Shamir described the two-hour session as "a very good and basic discussion" of the essential issues.

Shultz told reporters the two leaders concentrated on the need for direct negotiations between Israel and the Arabs and "how they might be structured."

Avi Pazner, a spokesman for Shamir, said the meeting was held in a "friendly spirit" but that differences remained over a U.S.-proposed international conference and Shultz's meeting last month with two Arab-American members of the Palestine National Council, the legislative arm of the PLO.

Shultz returned to the region without support from Israel, Jordan, or Syria, the three key parties, on his plan for negoiations to address an overall Middle East settlement in December, in the second stage of the talks.

He emphasized on his arrival Sunday that negotiations would be based on U.N. Security Council Resolution 242, which calls on Israel to yield territory captured in the 1967 Middle East war with Egypt, Jordan and Syria.

Shultz said the resolution, which also promises Israel security, applied to "all fronts." The resolution, however, does not specifically call on Israel to give up all the territory.

Asked if he agreed with Foreign Minister Shimon Peres that Israel should not return to its pre-1967 borders and that there would be no Palestinian state, Shultz replied: "Absolutely."

A reporter asked again if Shultz was saying "no" to a Palestinian state. Shultz responded: "No to a Palestinian state, no to a return to the borders."

Israel relinquished the Sinai Peninsula to Egypt as a part of a 1979 peace treaty. But Shamir is reluctant to give up the West Bank, which Jordan occupied from 1949 until 1967 when Israel captured the territory in a war.

Shultz's visit comes after four months of rioting in the occupied West Bank and Gaza Strip that has killed more than 135 Arabs and one Israeli soldier.

Shamir, in a tour of the West Bank on Sunday, questioned whether the Arabs were ready to deal with Israel. Shamir said he was skeptical "about all the prophecies that the talks will have some kind of result, a breakthrough."

Shultz also will meet with Peres and Defense Minister Yitzhak Rabin.

In Tunis, meanwhile, the PLO reaffirmed its rejection of the U.S. plan for talks on self-rule beginning May 1 and on the overall settlement in December.

The Palestine Liberation Organization's Executive Committee issued a statement Sunday saying the Palestinian people were unanimous "to thwart the dangerous American plan."

"The just and global solution must be based on the achievement of the national right of the Palestinian people, under the direction of the PLO, its sole legitimate representative," the statement said.