The United States, as part of an international effort to ease the plight of passengers on the standed ship Hai Hong, has offered to admit 2,500 more Vietnamese refugees from temporary camps in Malaysia, administration officials said yesterday.

Justice Department officials said the U.S. offer was approved late last week by Attorney General Griffin B. Bell after consultations with members of Congress and was passed to the Malaysian government through diplomatic channels on Saturday.

Reports from the Malaysian capital of Kuala Lumpur said the government is expected to allow the Hai Hong to remain anchored offshore while diplomats try to work out the future of its 2,500 passengers. The reports followed a day of meeting of senior Malaysian officials with diplomats from the U.S. Canadian and French embassies as well as a representative of the U.N. high commissioner for refugees.

Although the number of additional refugees to be admitted here is the same as the number aboard the ship, it appears unlikely that all the Hai Hong's passengers will land in the United States. If the Vietnamese from the ship are allowed to land in Malaysia, they will have to get in line for U.S. admission with 35,000 refugees already in camps there, the Justice Department said.

France and Canada have agreed to admit additional refugees from Malaysia as an inducement to that country to permit the hungry passengers, many of them sick, to take temporary shelter there, according to official sources. News reports said Belgium, West Germany, the United Kingdom, Switzerland and the Netherlands will take a few refugees who have relatives there.

The passengers on the rusty freighter have been anchored off Malaysia for 12 days waiting to hear they will be admitted to refugee camps there, sent to other countries or, as Malaysia threatened if no homes can be found for them, towed back to international waters.

The Hai Hong "boat People" have attracted worldwide attention because of the size of the ship and because of reports that they arranged their exodus from Vietnam by payments in gold to government officials there. The passengers have been described as mostly well-to-do people of Chinese orgin, but State Department officials said there are now some indications of more ethnic and economic diversity.

The Justice and State Departments are reported to be considering plans to double for one year the present annual immigration quota of 25,000 Indochinese. That would be a substantial effort to deal with the rising number of refugees.

The additional 2,500 people to be admitted here from Malaysia under the attorney general's "parole authority" would be in addition to about 10,000 Indochinese expected here from Malaysian camps this year.

Malaysia has also been told in recent days that U.S. procedures will be accelerated in an effort to bring out refugees from camps there more quickly, according to officials here.