Soviet transport planes flying into an air base north of the capital and additional Soviet advisers summoned from the field to posts in several ministries have generated new speculation and concern in U.S. government circles about Afghanistan, where a revolutionary government took power in a coup one month ago.

Despite statements by ranking officials of Pakistan and Iran that their neighbor has gone communist, State Department officials familiar with the area said it is far from certain that Afghanistan will become a Soviet satellite and that a number of recent Afghan deeds and words indicate that it will not.

In an effort to keep the Afghan options open, the Unites States has reorganized the new regime and informed the leaders it is prepared to continue economic aid, which has been about $20 million yearly, U.S. Ambassador Theodore L. Elio Jr. has been given a friendly reception by leaders of the new government in a continuing round of talks.

"Every time anybody moves in Afghanistan people say that there's a communist coup afoot," said Louis Dupree of the American Universities Field Staff, a leading U.S. expert who has spent much time in that country over the past 30 years.

Dupree, along with governmental experts, noted that the previous coup in July, 1973, by Mohammed Daoud generated a similar round of well-publicized worry that the Soviets were taking over - but that as time went on, the "revoluntionary" Daoud regime showed itself to be genuinely independent.

The present ruling group is clearly more radical than Daoud in its program and rhetoric, and it represents a clear break from the elite group of the Mohammadzai clan which has run the country for 150 years. The new government, headed by Nur Mohammed Taraki, is the creature of the leftist People's Democratic Party, which had been on the fringes of political life since its formation 12 years ago.

Though avowedly revolutionary, the party reportedly was not accepted as a communist party by Moscow. Accounts of the April 27 upheaval obtained by U.S. officials in the intervening weeks indicate that the Soviet Union had not part in preparing or executing the coup, though Washington officials believe the Soviets may have been informed in advance that it was to take place.

Moscow immediately recognized the new government, and has signed four civil aid pacts worth about $16 million as well as a trade agreement with the Taraki regime. The former government had been discussing these programs with the Soviets before the coup.

On his first trip abroad, to a meeting of "nonaligned" nations in Havana, Foreign Minister Hafezollah Amin stopped overnight in Moscow. A communique issued after a meeting with Soviet Foreign Minister Andrei Gromyko was scrutinized by American experts and found to be virtually the same as that issued by Soviet and Indian foreign ministers after the recent change of government there.

According to Dupree, 10 of the 21 ministers of the new government received some of their education in the United States, while three of the ministers, all military officers, received education in the Soviet Union.

Many of the new ministers are neophytes to major government responsibility, and important segments of their bureaucracies were ousted in the coup. The need for expert help is believed to account to part for the reported reassignment of Soviet advisers from the countryside to several ministries, including defense and mining, in Kabul.

About 1,000 Soviet personnel, including several hundred military personnel, were in the country under the old regime along with lesser numbers of advisers from other nations. Most of the 60 advisers from the United States are expected to remain. United Nations advisers are reported to be back at work on an anti-narcotics program, and West Germans have been asked to stay on as police advisers.

U.S. officials have no authoritive explanation for the flights of Soviet transport planes to Bagram Air Base, about 40 miles north of Kabul, reported by U.S. intelligence. Some reports suggest the aircraft contained military and communications gear. Major military equipment from the Soviet Union has traditionally come across the Afghan-Soviet border rather than by air, but there are no reports of such land movements so far.

The assessment in Washington is that the new government will certainly lean toward the Soviet Union more than the previous regime, but the unanswered question is how great the tilt will be. One governmental expert used the hands of a clock to illustrate his estimate, saying that if the Soviet land is on the hour, the old regime might be placed at 6 and the new regime between 8 and 10. He, like others, pointed out that Afghanistan has had historic close relations with its Russian neighbor but at the same time has placed high value on its independence.

Raraki and other officials have spoken since the coup of "positive neutrality" in foreign affairs, and said Afghanistan's relations with other nations will be determined by the extent of their political and economic support. The officials said Afghanistan will not accept aid with strings from any nation.

Pakistan is particularly sensitive to political changes in Afghanistan because of a long-standing dispute over the tribal territory known as Pushtunistan between the Afghan border and the Persian Gulf. Early broadcasts by the Afghan government radio, including praise for the coup by separatist leaders across the border, caused alarm in Pakistan. Apparently to allay the concern, Afghan broadcasting in the Pushtun language has been recently reduced to one hour per day from four hours, according to officials in Washington.

When the coup took place a month ago, a team of officials from Cities Service Oil Co. was en route to Kabul to negotiate an agreement for oil exploration in southwestern Afghanistan.Their flight was halted short of the capital, and nothing has been heard since about the exploration program. U.S. officials believe the fate of that plan will be another signal of the direction that the new regime in Afghanistan is taking.