Vietnam has received commitments for perhaps more than $6 billion in economic aid over the past two years, according to some analysts.

Almost $3 billion could come from the Soviet Union. The United States, which tried to block a Communist takeover of Vietnam for 25 years, will be providing aid indirectly through various international organizations.

Hanoi's record in seeking out and obtaining financial support over the past two years has been remarkable. None of the specialists interviewed could recall any country having receiving pledges of so much economic aid within such a short period of time.

Bangladesh, which was economically prostrate after winning independence from Pakistan five years ago, received promises of $3 billion in assistance in the four-year period 1972 through 1975, Bangladesh has about 80 million people; Vietnam about 46 million.

The estimate of aid going to Vietnam is only a rough approximation. There is general agreement that Hanoi has been promised at least $3 billion. The $6 billion figure is based primarily on the strong endorsement given Vietnam's 1976-1980 economic plan by the Soviet Union. Estimating the totals is complicated states of not disclosing the value of aid being given other Communist nations.

Analysts agree that Hanoi's campaign for international assistance has been agressive, flexible and pragmatic. In its quest, Vietnam has muted its criticism of Asian states still closely linked with the West. It has also dropped its earlier refusal to accept multilateral assistance and actively sought help from such organizations as the United Nations and the Asian Development Bank.

The World Bank and the International Monetary Fund announced recently that they were embarking on assistance programs for Vietnam.

The United States has generally voted against programs for Vietnam in such international groups. Washington has said it will not honor a pledge of $3.25 billion in aid made by former President Nixon at the time of the 1973 Vietnam cease-fire agreement on the grounds that North Vietnam violated that agreement with its victorious 1975 military offensive against the U.S. supported government in the South.

The level of assistance Moscow seems prepared to give Hanoi is regarded as a reflection of the importance the Soviet Union places on Vietnam in the context of Moscow's rivalry with China. Reports from Hanoi indicated that the Soviet influence there appears much greater than China's.

Peking has indicated a certain coolness toward Vietnam since its conquest of the South, presumably because of the emphasis. Hanoi has placed on its relationship with Moscow. Another source of strain between the two Asian Communist states is their rival claims to potentially oil-rich areas of the South China Sea.

There is considerable obscurity surrounding China's aid program in Vietnam. A projection by the First National City Bank has it supplying $1.5 billion through 1980. Yet, in mid-1976 there were persistent reports from Peking that China had stopped all aid to Vietnam. In September 1975, however, there was an announcement that a new economic aid agreement between the two countries had been signed.

Vietnam Communist Party leader Le Duan paid a visit to Peking that same month but left without issuing the customary joint communique. One analyst says there is reason to think that China is limiting itself to funding projects that were begun earlier and has not agreed to finance anything new.

Compared to what it is getting, or expected to get, from its two major Communist patrons, Vietnam will be getting little from other countries: $12 million form Cuba, $45 million from the Netherlands; $9 million from Norway; $6 million from Algeria; $2 million from West Germany and $49 million from U.N. Development Program (for the period 1977 through 1982). Small as the separate figures are, the toal of such aid is approaching $1 billion, with new programs announced almost every week.

One of Hanoi's objectives is thought to be a lessen its dependence on any single source of aid. Another is believed to be a search for the sources of the best available technology.

Although Vietnamese officials have impressed foreign negotiators with their technical skill and realism, some doubts have been expressed about the country's ability to absorb the amount of aid promised.

Decisions on projects are made by a small interagency group of key officials which reportedly moves slowly. This has resulted in starting dates being delayed for two years of more with substantial modifications being ordered in a project in mid-construction.

There is a report that lumber will had reached an advanced stahe of planning before the foreign technicians learned that the site had no access roads. The project was reportedly held up six months while the roads were built.

Vietnam has shown a decide preference for completely equippedfactories which the donor country supplies right down to the doorknobs and fire extinguishers. Such projects are no drain on Vietnam's economy.

Vietnam has permitted some foreign companies to resume the-communist joint-venture operations in South Vietnam. Matsushita Electric of Japan, for one, is again producing radios and television sets at its old plant near Saigon.