U.S. proposals for economic and military aid to Pakistan are being greeted with deep distrust by leaders of Pakistan's troublesome province of Baluchistan, amid signs of smoldering opposition to the central government and a reservior of popular sympathy for the Soviet Union.

Thrust into the geopolitical limelight by the Soviet invasion of Afghanistan, Baluchistan is in a frontline position in U.S. and Pakistani efforts to contain feared Soviet expansion southward.

But dissident tribal and political leaders in this Baluchi provincial capital make it clear that they are determined to extract a political and economic price for Baluchistan's acquiescence in its new strategic role. If the price is not met, they indicate, this province's predominantly antigovernment Baluchi tribes may be prepared to seek Soviet help in futhering long-suppressed goals of regional autonomy or independence.

In that event, the arms the Carter administration is trying to rush to Pakistan's president, Mohammed Zia ul-Haq, would probably wind up being used against the Baluchis.

Furthermore, a concerted effort to arm Afghan Moslem rebels in response to Moscow's intervention would probably entail a retaliatory Soviet subversion campaign in Baluchistan, possibly leading to the disintegration that U.S. economic and military aid is designed to prevent.

The U.S. dilemma is compounded by widespread opposition to Pakistan's military ruler, generally regarded as the most unpopular leader in the country's 33-year history as an independent nation.

Talks with opposition figures here and elsewhere in Pakistan indicate that, unless the U.S. military aid is coupled with pressure on Zia to hold long-promised elections, it will be seen as confirmation of U.S. support for a dictatorial ruler and will further alienate the population.

That view is held especially strongly here in Baluchistan, where opposition figures fear that new U.S. arms will be used to tame permanently independent-minded and often rebellious Baluchi tribesmen. As a precedent, dissidents cite the use by Iran of U.S.-supplied helicopter gunships in helping Pakistani forces combat Baluchi guerillas during a 1973-77 war in this vast, arid territory bordering the Arabian Sea.

"If the U.S. gives aid to Pakistan, it will not be for the people, but to to strengthen the Army Junta," said a leading Baluchi sardar or tribal chieftain.

The little-reported but bloody four-year war left bitter memories on both sides. More than 3,000 Pakistani troos and at least 5,000 Baluch guerrillas are estimated to have died in the fighting, which involved as many as 55,000 Baluchi tribesmen and 70,000 Pakistani troops at its peak.

The war ended in November 1977, when Gen. Zia overthrew the former prime minister Zulfiqar Ali Bhutto, who was later hanged. Zia then reached a truce agreement with Baluchi leaders.

The insurgency raised fears in Islamabad and Tehran that the more than two million Baluchi tribesmen living in a 207,000-square-mile region that straddles southwestern Pakistan, southeastern Iran and southern Afghanistan could unite and try to establish an independent state with help from the Soviet Union. However, there was no sign of any serious Soviet commitment to the rebellion at the time.

Lately, Iranian Baluchistan has been considerably more restive than Pakistani Baluchistan, although the latter has traditionally had more militant and better organized leadership. Pakistani Baluchistan is also the bigguest of the three Baluchi areas: the Baluchi tribal region covers 134,000 square miles and comprises 40 percent of Pakistan's land mass.

Baluchi leaders have complained bitterly that since the rebellion, the central government has neglected Baluchistan economically, and effectively imposed a military occupation by ethnic Punjabis from the eastern part of the country. Punjabis represent major ity of Pakistan's population of 75 million, and dominate the country's armed forces and political leadership. The most prominent Punjabi is President Zia himself.

"Suppose the Russians come in and drive to the coast, the leading sardar here said. "What do we have to lose? We have never been given anything except hefty chains. At worst, we would exchange one set of chains for another."

A political opposition figure who is also active in Quetta said, "Some people might view the arrival of the Russians as a ray of hope. They want to be liberated from this martial law, hwhich is absolutely stifling."

Because of martial law restrictions on their public statements, neither man wanted to be named.

The sardar an imposing figure with a mane of white and gray hair, handlebar mustache and clipped white beard, expressed considerable sympathy for the Soviet Union, but insisted he was not a Marxist -- merely a Baluchi nationalist. By his own and other accounts, he is not the most radical of the major Baluchi tribal leaders.

The views of four Baluchi tribal leaders are considered important in assessing the mood of Baluchistan, since they collectively command the loyalties of 300,000 to 400,000 of the province's estimated 1.6 million Baluchis.

The most prominent of the sardars is Khair Bakhsh Marri, the leader of the Marri tribe whose 115,000 members make it the biggest single Baluchi grouping in the province. Marri is also widely considered the most radical leftist of the major sardars, although there is some debate about whether he is actually a communist.

Marri's and other sardars' espousals of Marxist beliefs may be just a question of "staying out in front of the youth," one senior Western diplomat in Pakistan said."I suspect they are a lot more sardar than Marxist."

Another avowed leftist is Akbar Khan Bukti, the hereditary leader of the Bukti tribe, estimated to number close to 100,000.

Considered somewhat more moderate are the sardar of the Mengal tribe, Ataullah Khan Mengal, and a leader of the Bizenjo tribe, Ghaus Bakhsh Bizenjo. The latter is a cousin of his tribe's sardar, but ranks as its most prominent political leader, described by associates as a card-carrying communist in his youth, Bizenjo is said to have mellowed greatly, while remaining a dedicated leftist.

According to a diplomat, all four leaders are "pretty well-heeled types."

Highly educated and well-traveled they speak good English and enjoy considerable wealth and the veneration of their tribesmen.

A much more radical element is the Baluchistan Students' Organization which has 1,500 to 2,000 members, and is said to have the sympathy of a majority of Baluchi students throughout the country.

There are rumors that the organization receives some funding from the Soviet consulate in Karachi, but these could not be confirmed.

In any case, the well-organized group is considered staunchly pro-Soviet, and the most amenable to Moscow's influence should the Kremlin undertake to stir up trouble in Baluchistan. Last fall, according to sources here, members of the organization participated in an anti-Zia demonstration in Quetta and displayed such slogans as "U.S.S.R.: Torch-bearer of liberation movements." Martial law courts convicted 18 students on charges stemming from the demonstration and sentenced them to floggings and jail terms, the sources said.

Another group that could be used in a Soviet attempt to subvert Baluchistan is a 4,000-strong contingent of the Marri tribe that fled to neighboring Afghanistan during the 1973-77 rebellion. Despite a general amnesty and a program of reparations declared by Zia in March 1978, fewer than 150 of the refugees have returned to Pakistani Bulachistan, one sardar said.

"All the hard-core guerrillas are still out of the country," he said.

Among the guerrilla leaders still resident in Afghanistan are Mir Hazar, who has vowed to take help from wherever he can get it to avenge losses suffered during the rebellion. Another is an ethnic Pushtun, Ajmal Khattak, a former leading figure in the outlawed National Awami (Free) Party -- the grouped antigovernment Baluchi and Pushtun tribesmen.

Khattak reportedly has organized a number of guerrilla camps in Afghanistan and counts about 700 militant Pushtun followers.

Pushton -- who account for about 1.2 million of Pakistani Baluchistan's total 2.8 million population, according to Pakistani officials -- inhabit a belt stretching from northern Baluchistan along the Afghan border into the neighboring North-West Frontier Province, where they make up the majority.