Secretary of State James Baker opened high-level talks on postwar planning Friday to prod the Arabs, pressure the Israelis and probe for softness in long-held animosities in the Middle East.

One source reported that the war has strengthened Saudi Arabia's willingness to play an active role in regional postwar peace and rebuilding efforts. Also discussed was creation of a permanent Arab gulf security force supplemented by U.S. naval power and military exercises.In talks with Saudi Foreign Minister Saud Abdual al-Aziz al-Faisal and later with King Fahd, Baker also sought hints of accommodation toward Israel.

During the next nine days, Baker will consult with officials of eight Arab nations, Israel and the Soviet Union on the challenges and opportunities posed by the battlefield defeat of Iraqi President Saddam Hussein.

Because Fahd gave the needed green light last August for the allied war effort, it came as no surprise Saudi Arabia was where Baker set out against formidable odds to sustain the political momentum of military triumph.

As he arrived at Riyadh Air Base, where Patriot missile batteries and AWACS radar planes stood as reminders of war, there was no clear evidence that festering regional problems were any more ripe than before for a diplomatic solution.

In a region where progress is measured in nuance and small increments, Baker said at the outset that he hopes to find interest in "confidence-building measures" - short of full recognition or formal negotiations - that could inch the Arab states toward peace with Israel.

In private, U.S. officials indicated those measures could be as basic as the start of informal dialogue, perhaps aimed at the establishment of some commercial or economic cooperation. Formal peace treaties, like the one Egypt signed in 1979, could come later and presumably would depend on Israeli concessions to Palestinian self rule.

Though Israeli Prime Minister Yitzhak Shamir has hinted at a willingness to open a dialogue with individual Arab countries, his strategy could be cleverly designed to avoid a head-on collision over the Palestinian issue on which he has shown no sign of give.

Deadlocked for more than two years over how and with whom Israel should settle the status of its occupied territories, the dispute has become embittered of late by wartime emotions.

Palestinian support for Saddam's Scud missile attacks infuriated the Israelis, stiffening Shamir's hard-line attitude and reducing sympathy for the Palestinian cause.

For his part, Baker will again urge Israel to accept the U.N.-mandated principle of swapping territory in the occupied lands for Arab guarantees of security. He also offered to meet with Palestinians in Israel next week.

Which Palestinians and what eventual role they might play was left unstated. Certain to be excluded is the Palestine Liberation Organization and its sympathizers, discredited by the PLO's backing of Iraq in the war.

On Saturday, Baker confronts the casualties and consequences of war with a visit to Kuwait City, where he will meet with leaders of the government struggling with the massive project of recovery and reconstruction that could cost as much as its prewar foreign holdings of $100 billion.