WASHINGTON (AP) _ A highly unusual project in which U.S. economic experts tried to help Liberia straighten out its chaotic governmental finances has ended abruptly, reportedly scuttled by Liberian President Samuel Doe.

One frustrated American participant said Doe could not be persuaded to abandon his practice of maintaining an extracurricular budget outside the government's control.

The premature termination roughly halfway into the two-year project, coming as it does on the heels of a congressional freeze on aid to Liberia, may be prompting Doe into action.

Doe, a former army sergeant who took power in a bloody 1980 coup, is considering a trip to the funeral of Japan's Emperor Hirohito in hopes of meeting President Bush, Liberian officials and dissidents say.

Although the evolving situation remains in flux, analysts are concerned it could prompt a renewal of threats against U.S. interests in the coastal African nation, which is supported largely by U.S. foreign aid and investment.

The project, which stemmed from Doe's efforts to boost U.S. support and introduce some order into his government finances, was billed as a $15.5 million program when it was signed in 1987.

The unusual arrangement, which gave American experts the right to cosign Liberian government checks, was made possible by the historic links between the United States and Liberia, a country of 2.3 million residents that was founded in the 19th century by freed slaves.

All but one or two of the 17 experts, who have stayed behind to complete computerization programs, are now back in the United States, said Fred Berger, Vice President of Lewis Berger International, which conducted the project under contract to the U.S. government.

The team was frustrated by lack of support from Doe and by his practice of maintaining a budget outside the government's control, Berger said.

A statement by the Agency for International Development said the project achieved progress in getting the government to meet its payroll on time, pay pensions and increase tax receipts. ''Unfortunately, progress was not uniform and some serious problems could not be resolved,'' said the statement.

Dissidents and congressional staffers said the team discovered that Doe manages part of the government budget like a discretionary slush fund which was outside the purview of the American experts.

A spokesman at the Liberian Embassy, Paul Yarl, declined to discuss the project, saying only that it had been completed in a satisfactory manner.

Specifically, revenues from the government-owned corporations for forestry and petroleum products - which account for about 40 percent of the state's income - were handled directly by Doe, said Amos Sawyer, an exiled Liberian political scientist who heads a dissident organization in the United States.

Doe uses these funds to cater to various whims, Sawyer said. For example, when Liberia's soccer team beat Ghana last year, Doe declared a national holiday and gave the team $1 million.

But Berger said Doe also used the money for public works projects and to pay back official bank loans.

Doe has not protested the recent setbacks in relations with Washington, said U.S. Embassy spokesman David Krecke in a telephone conversation from Monrovia.

But there is concern that Doe may renew past threats against U.S. communications facilities and military access rights, officials said. They spoke on condition of anonymity.

Liberia experts say he has not acted on these threats in the past because too much of his economy depends on American investments.

The United States has been the bulwark of Liberia's economy, pouring $434 million in financial aid between 1980 and 1986. There also is some $400 million worth of private U.S. investment in Liberia, much of it in rubber plantations, iron ore mining and forestry.

The United States maintains a relay station for Voice of America broadcasts to Africa and southern Europe, officials said. There is also a diplomatic communications facility that handles traffic from U.S. posts in Africa to the United States.

The U.S. Coast Guard is involved in running a tracking station for navigation in the region, officials said.

Economic aid to Liberia, which suffers from a crushing debt burden and foreign exchange shortages, was frozen last year after the State Department failed to certify that the country had made progress in rectifying human rights abuses, officials said.

As a result, Congress has so far withheld $22 million in aid - about one- third of the funds allotted to Liberia, according to AID.

The State Department's recently released report on human rights says Liberia's record ''was set back in 1988 by several adverse developments,'' including the unexplained deaths of several men while in detention for unsubstantiated charges of plotting a coup.