US Plays Catch-Up on Cambodia. With Vietnamese troops leaving, US weighs options to promote a noncommunist regime. FOREIGN POLICY

UNITED STATES policy toward Cambodia is beginning to evolve rapidly as Washington tries to stay up with the very fluid situation in Indochina. Tomorrow Prince Norodom Sihanouk, leader of Cambodia's noncommunist resistance, meets in Jakarta with Prime Minister Hun Sen of the Vietnamese-backed People's Republic of Kampuchea (PRK) to discuss new peace offers from the Cambodian communist leader.

In two weeks, the leaders of China and the Soviet Union will meet with Cambodia as the main agenda item.

Today Prince Sihanouk is slated to meet with Vice-President Dan Quayle, who is visiting the region, to discuss the state of efforts to find a formula for internal reconciliation in Cambodia and the pull out of Vietnamese troops.

The subject of possible US lethal aid to Sihanouk's forces may well come up. The Bush administration is seriously reviewing a range of options, including giving the Non-Communist Resistance (NCR) lethal aid, to increase the NCR's leverage as the situation moves toward possible settlement, say US officials and congressional aides.

Vietnam and the PRK have unilaterally announced that all Vietnamese troops will leave Cambodia by Sept. 30. But there has been no progress on an internal settlement between the four Cambodian factions - the PRK, the two noncommunist parties, and the notorious Khmer Rouge.

Vietnam and its Cambodian ally are trying to generate momentum for international recognition of the PRK regime, US officials and specialists here say. They would like to entice/pressure Sihanouk to lend his legitimacy to their plans, they say, but no one questioned here thinks the PRK is yet ready to offer enough to win the prince's support.

The key issue right now, says Frederick Brown, an Indochina specialist in Washington, is whether ``Vietnam is going to be able to push a revised PRK down the throat'' of the noncommunist resistance and their supporters, including the US.

US officials say they are not tempted. ``The greatest flaw in this effort,'' says a US diplomat, ``is that the PRK regime doesn't have the wherewithal to guarantee peace - it's a formula for increased civil war.'' Peace, he says, requires a solution that involves most, if not all, of the warring parties and has the backing of their outside supporters to guarantee the agreement and end arms flows.

Nevertheless, the Cambodia situation seems ripe for progress. In this context, the US is reviewing its options. In addition to possible lethal aid, the Bush administration is looking for ways to prepare an international framework for overseeing and guaranteeing an eventual accord as well as to mobilize an international reconstruction effort, they say.

``It's a question of deciding where we can make an impact that will matter,'' a US official says, since the US has limited direct leverage on the situation. This requires a complicated balancing between US goals of getting the Vietnamese troops out, allowing a representative Cambodian regime to emerge, all the while preventing the notorious Khmer Rouge from returning to power.

The House Foreign Affairs Subcommittee on Asian and Pacific Affairs, chaired by Stephen Solarz (D) of New York, is recommending removal of the existing cap on US aid to the noncommunists and is urging the Bush administration to seriously consider lethal assistance.

Mr. Solarz has also suggested a major United Nations role, similar to its undertaking in Namibia, as part of a way to move from civil war to free elections in Cambodia. While US officials note the difficulty in arranging such an effort, they welcome the Solarz concept. ``There's a real need for creative thinking'' to move the situation along, the US official says.

Mr. Quayle and top officials that follow Asia are conferring this week with the leaders of the Association of Southeast Asian Nations (ASEAN) on Cambodia. Quayle has already run into opposition to the idea of US lethal assistance from Australian Prime Minister Bob Hawke. Mr. Hawke reportedly feels more arms can only worsen the situation.

But many in ASEAN are likely to be supportive. A Thai official reached by phone says the US is the only superpower that can help guarantee a role for the NCR against two better-armed communist forces.

``The point is not how many guns the US sends but the symbolic gesture of support,'' he says. ``This will be a strong signal that the US is close to the process and ready to intervene for the interests of the free nations of Southeast Asia. ... To the degree that US aid can also strengthen the NCR against the Khmer Rouge, that is great, too.'' The US also has to put Cambodia high on its diplomatic agenda with China and the Soviet Union to help keep the diplomatic track moving, he says.

Such a position by Thailand is particularly important, US and Chinese officials say. Only a few weeks ago it looked as if Thailand might break ranks and seek accommodation with the PRK. If that happened, then American, ASEAN, and Chinese leverage on the situation would be greatly undermined, says Mr. Brown, the Indochina specialist. Thailand has been the supply support base for the NCR and the Khmer Rouge.

Thai sources say they now feel they were burned by inviting PRK leader Hun Sen to Bangkok because he only used the opening to adopt a more ``arrogant'' position on internal reconciliation in Cambodia.

Mr. Brown, who recently visited Cambodia with a delegation from the Council on Foreign Relations (a private foreign policy group), says it is clear the Hun Sen regime is ``thrashing socialism'' economically in an effort to create a popular constituency. But it remains to be seen how deep popular allegiance is and what the regime's real political orientation is.

Some in the US already contend that the Hun Sen regime is showing enough potential independence and effectiveness at home to warrant US overtures. Bill Herod of the nonprofit Indochina Project, for example, says the most sensible solution is a compromise between Sihanouk and Hun Sen. The prince can bring international legitimacy and aid while Hun Sen has a functioning civil and military bureaucracy.

Jeremy Stone, president of the Federation of American Scientists, returned from a recent visit to Cambodia arguing that the US emphasis should be to prevent a return to power of the Khmer Rouge and that the PRK regime is the best bulwark against it. ``I reached the conclusion that this government is as good as Cambodia ever had,'' he says and that any hope for a four-party coalition government among the warring factions ``is `Alice in Wonderland.'''

In weighing lethal aid, the administration is considering that the NCR now has more troops than arms for them, a US diplomat says. Congressman Solarz argues that the NCR could double its troop size by year's end if given enough arms and training.

The Bush team is also considering how much political weight this move could add to the non-communists' bargaining position at this crucial time, the diplomat says, and what impact the arms might have in helping the NCR stand up to the Khmer Rouge in any post-settlement situation.

Most US specialists questioned say the prospects for renewed fighting after a settlement are high.

``If we are serious about wanting some sort of noncommunist outcome in Cambodia,'' says a well-placed congressional aide, ``then the response is to help equip them for the coming struggle even if we're late in doing it.''