The Museum of the American Indian, squeezed into a tiny out-of-the-way building in upper Manhattan, needs a new home. Everybody agrees on that. And not much else.

The museum's directors would like to move the collection into the Custom House, a federal property in lower Manhattan. But New York City officials have not decided whether the plan makes financial sense. As a result, the directors are threatening to move the whole collection to Washington.

The museum owns the largest collection of anthropological artifacts in the world. But due to space limitations, most of its collection sits, unseen, in a Bronx warehouse.

As the dispute becomes increasingly acrimonious, the Smithsonian Institution finds itself cast in the unattractive role of the "seducer of other cities' important cultural resources."

That was the charge made by Rep. Bill Green (R-N.Y.) this week when he learned that the Smithsonian was still pursuing a plan that may lead to the construction of an American Indian museum on the Mall.

The Smithsonian feels itself wronged.

"The preservation of the collection and sharing the riches of that resource as widely as possible is a personal as well as institutional concern," said Smithsonian Secretary Robert McC. Adams yesterday. "The geography of resolving that concern is less important than the resolution, a goal toward which the Smithsonian seeks only to be helpful."

The dispute until now has primarily been between the museum's board of directors and city and state officials in New York.

The museum's directors said that unless city and federal officials make the Custom House available, they will attempt to move the museum to Washington.

That requires the New York Supreme Court to set aside a restriction in the trust of George Heye, founder of the museum, that it remain in the state.

State Attorney General Robert Abrams said he would fight any effort to move the museum.

"The attorney general charges that the museum board is being recalcitrant and obstructionist," said Abrams' press secretary David Fishlow.

He said museum President Roland Force is "failing to carry out his responsibility to the museum and the community. Roland Force said keeping the museum in New York is not in the best interest ... of the collection. He is unwilling to pursue some very practical possibilities."

Untrue, said Edward Costikyan, the museum's attorney. "This is just not accurate. We have looked at so many possible sites. None meet our requirements, and our requirements are not something we made up. We have the world's largest collection of anthropological artifacts . . . and it's sitting in a warehouse in the Bronx."

Costikyan said only two sites meet the museum's need for approximately 400,000 square feet of space -- the Custom House and the proposed museum that would be built and funded under the auspices of the Smithsonian. That building would sit on the Mall, between the National Air and Space Museum and the Botanical Gardens.

"If the Custom House is available, the Washington move is not legally permissible," Costikyan said.

Sen. Daniel P. Moynihan (D-N.Y.) held a meeting in New York yesterday in an attempt to break the stalemate and keep the museum in New York.

"I want the museum to stay in New York and I thought we had a proposal to do that," he said, referring to the Custom House plan. But, he said, the meeting gave him little to be cheerful about. He said that proposal had been on the table since February, but no action had been taken. "I don't know if we have the civic energy," he said.

Robin Solomon, executive assistant to Sen. Alfonse D'Amato (R-N.Y.) said his boss is not sure about the wisdom of a move to the Custom House.

"He's skeptical until shown otherwise," he said. "The museum wants their arrangement and their arrangement only."

Noting that President Reagan and Congress were both disposed toward moving the museum to the Custom House, but that the next president and Congress might feel otherwise, Moynihan told the disputants: "You have 18 months, and that's it."