The United States, loading ever more peacemaking duties upon its new-found friend the United Nations, has yet to make a dent in the $718 million debt it owes the world body.

The Bush administration has promised to pay all its arrears, but U.N. diplomats are holding their counsel. Full payment will be a critical standard by which to judge the reborn U.S. commitment to the United Nations, they say.U.S. officials are quick to point out that the U.S. government still pays far more than any other nation.

The United Nations says the U.S. government owes $567.7 million to the general budget, including arrears.

The United States owes an additional $150.1 million for peacekeeping duties, U.N. officials say. The United States maintains its total back dues are $132.4 million, with an additional assessment for 1991 of $68.9 million dollars.

That does not include the newest Iraq-Kuwait observer group, expected to cost the United States about $38 million, 31 percent of the total cost for the first year. The United States pays about 31 percent of all U.N. peacekeeping operations funded from assessed contributions - more than any other nation.

Total U.N. budget arrears are $1.12 billion for the $1 billion annual budget. Nations currently owe $357.5 million for six peacekeeping operations, financed by separate, non-budget assessment.

Of the annual $1 billion general U.N. budget, the United States contributes one-quarter, the highest assessment of any nation.

But in 1990 the U.S. government paid a total of $1.12 billion to the United Nations and its agencies, including $108 million for U.N. peacekeeping and $112 million for U.N. refugee programs.

Its contributions include payments to the U.N. Children's Fund, the U.N. International Atomic Energy Agency and the Pan American Health Organization.

The United States, which a decade ago sharply criticized the world body as a Soviet tool and Third World debating society, rediscovered the East River enclave during the gulf crisis and found the U.N. system worked handily for U.S. political ends.

While the administration is committed to paying its U.N. dues and arrears, Congressional leaders said Monday that budget constraints may make this impossible.

John R. Bolton, assistant secretary of state for international organizations, appealed to Congress for full U.N. funding.

"Unless we receive this appropriation, our allies will perceive our inaction as abandonment of interest in crucial (U.N.) reforms, and those skeptical of our motives . . . will trumpet non-payment of our arrears as clear evidence of U.S. unreliability. We cannot afford to let this happen," he told Congress.

"President Bush is fully committed to making all our current payments and arrears, and we intend to work closely with the executive branch and Congress on ways and means to ensure that our U.N. obligations are fully funded," a State Department official said.

Over the years, longstanding policy differences have led the United States to withhold some U.N. assessments, including those aiding the Palestine Liberation Organization, the South-West Africa People's Organization and the Law of the Sea treaty agency.

The latest U.N. tab will cover the newest U.N. peackeeping mission - a 1,440-person observer group on the Iraq-Kuwait border. The United States has promised to pay its share, along with Britain, China, France and the Soviet Union, which will be serving together for the first time.

The United States is not the only debtor. The Soviet Union owes $109 million on the current budget and $83.4 million for peacekeeping duties last year, plus $77 million it still hasn't paid from the U.N. Congo peacekeeping force of the 1960s.

Other debtors include Britain, $33.5 million; France, $28.7 million; Brazil, $24.8 million; Germany, $43 million; Iran, $10 million; Iraq, $1.1 million; Israel, $4.9 million; Japan, $101 million; Saudi Arabia, $9.3 million; and South Africa, $45 million.