The Carter administration, despite its publicized opposition to the political takeover of South Korea by a group of generals, has permitted the head of a U.S. government bank to visit Seoul this week to discuss expanding economic cooperation.

Although officials declared yesterday that no political meaning was intended, there is little doubt that the visit of John L. Moore, chairman of the Export-Import Bank, is being read as a sign that the United States is not prepared to exert strong pressure on the Seoul generals to loosen their grip.

State Deparment officials said the mission by Moore was considered during last weekend's high-level policymaking meetings about Korea. An official said Moore was allowed to proceed to Seoul on Monday because "there was no clear policy against it" and because his trip had been previously scheduled.

Another official, terming the decision "a tough call," said the Moore mission had been reduced in duration and visibility because of concern about the political situation in Seoul. Moore was permitted to go, the source said, after his strong pleas that he had to protect $3.1 billion in Export-Import Bank investment in Korea, the largest of any country.

President J. Bruce Llewellyn of the Overseas Private Investment Corp. (OPIC), another U.S. government credit agency operating abroad, canceled plans for a trip to Seoul this week, according to official sources. The decision to cancel this trip was made at an earlier stage of U.S. policy deliberations.

A number of American-based commercial banks have made clear in recent weeks their reluctance to grant new loans to Korea. The shaky nature of the Korean economy contributed to the reluctance among some U.S. policymakers to do anything that might lead to economic panic. This was among the arguments in support of the Moore mission, sources said.

The high policy councils of the administration previously had foresworn any action in the current political crisis that might seem to weaken U.S. support for Korean security, because of the danger that this might generate pressures or even a military adventure by North Korea.

In a decision apparently related more to operations than policy, the Pentagon announced that the aircraft carrier Coral Sea and three accompanying ships have left the waters near Korea to resume their journey to the U.S west coast. The ships were diverted toward Korea as a gesture of warning to North Korea during the turmoil in the South Korean city of Kwangju.

U.S. leverage on the Seoul generals, with military gestures ruled out, is limited to economic and political actions and signals. And the decision to permit the Moore mission to visit Seoul this Monday through Wednesday is a sign of the difficulties of -- and resistance to -- employing the available economic and political clout.

Reports of the policymaking about the Export-Import mission to Seoul circulated as the State Department announced that Secretary of State Edmund S. Muskie will make his initial official visit to Asia late this month. Muskie will attend the foreign minister's meeting in Kuala Lumpur, Malaysia, sponsored by the five-nation Association of Southeast Asian Nations (ASEAN) June 27-28.

Muskie's decision to attend, despite his stated reluctance to spend much time in travel, was attributed to his desire to show appreciation for ASEAN support of the United States on Iran, Afghanistan and other issues.

Muskie is planning to attend the seven-nation economic summit with President Carter in Venice and a foreign ministers' meeting of NATO countries in Ankara immediately before his trip to Asia.