MANAGUA, NICARAGUA -- Last spring, President Bush described a $300 million U.S. aid package to Nicaragua as so urgent that he warned Congress against taking its Memorial Day vacation until it was approved. "With democracy at stake, there is simply no time for delay," the president declared.

But six months later, less than a third of the money approved by Congress has been disbursed and no new aid has been earmarked for Nicaragua in 1991. Nicaraguan and international officials are accusing Washington of moving slowly to assist a nation holding tenuously to democracy.

There have been delays in the delivery of funds to finance the purchase of foreign oil and to help relocate former members of the U.S.-backed contra guerrillas who laid down their arms this spring.

The oil money, due in early November, arrived a month late. In the case of the contras, a delay in U.S. funding meant a suspension in the delivery of tin roofing and clothing for former rebels and their families who are starting new lives in Nicaragua after eight years of war.

Some non-American diplomats suggest that the aid delays are a symptom of flagging U.S. interest in Nicaragua -- a sharp departure from the Reagan administration's proxy war against the Sandinista government and the Bush administration's decision to aid openly the presidential campaign of Violeta Chamorro, who defeated the Sandinistas in February's election.

Most agree that the sense of urgency that Bush cited in his appeal to Congress has evaporated, even though Nicaragua's economy has barely braked its free fall.

"If you look at what the U.S. has done since the elections to ease Chamorro's way, it doesn't seem to be enough," said a Latin American envoy.

"We were under the illusion that this was a preferential case and that the bureaucracy would take notice and act with great speed," said Vice President Virgilio Godoy. "What we are seeing is another thing: business as usual."

U.S. officials insist that aid to Nicaragua remains a top priority and that the rate of delivery is torrid compared to elsewhere.

"I think this has to be one of the fastest starts for any program anywhere in the world," said a U.S. official. "We went from zero to $100 million in six months." About $260 million of the $300 million package is expected to be delivered by October 1991, he said.

Another U.S. diplomat defended the progress in delivering the aid but added, "Dumping that $300 million in here is not what the Congress had in mind -- and it was approved before Iraq and Kuwait changed the equation."

Godoy and other Nicaraguan officials said the U.S. aid, while generous, will not compensate for the loss of the assistance Nicaragua formerly received from the Soviet Union and Eastern Europe.

Concern about the aid coincides with mounting indications that the economic recovery promised by officials of Chamorro's government when they took office April 25 is slower than expected. Some economists say the economy may shrink by 2 or 3 percent this year.

While some new businesses are opening and Managua shows a certain commercial bustle, the nation's unemployment rate remains at 40 percent and inflation, while down sharply from the spring, is still more than 300 percent annually.

The Chamorro administration, moving to cut a deficit that was running at $26 million a month in April, ended subsidies on telephones, electricity and public transportation. This trimmed the deficit to $6.8 million in September, but it also sent prices soaring. The result: Nicaragua, one of the poorest countries in the region, also became one of the most expensive, with prices in many instances to rival Miami's.

The government's economic program has been further undermined by strikes in May and July by government workers allied with the Sandinistas. The strikes forced the government to abandon plans to trim the public payroll by firing government workers and frightened off potential foreign investors.

Nicaraguan officials had some success in drumming up assistance from other nations to cover a trade deficit. They secured a $120 million pledge last spring from a group of industrialized countries meeting in Rome. But little of that money has been delivered so far.

Last week international donors at a meeting in Paris rebuffed Nicaragua's requests for another $300 million to pay off debts to the World Bank and the Inter-American Development Bank. The United States has already promised $50 million to help with the debts.

After Bush signed the U.S. aid package May 26, $60 million was sent to Nicaragua almost immediately, mostly to finance the purchase of imported oil, and monthly installments of $5 million began flowing to the Organization of American States to aid in repatriating contras.

But the contra funds, which include agricultural and building supplies as well as food, clothing and $50 in cash for each former combatant, stopped in October, tangled in red tape in Washington, according to OAS officials here.

U.S. officials said they held up the $20 million in aid for oil purchases to await the outcome of a five-week bargaining session between the government and Sandinista opposition leaders.

The session produced an "Economic and Social Consensus," signed Oct. 26, in which the government won acceptance for a broad privatization program in exchange for scrapping plans to fire 10,000 to 15,000 public employees -- about a tenth of the Sandinista-dominated government work force.

Some U.S. officials wondered aloud if any American aid package would be sufficient to deal with Nicaragua's economic problems, fueled by eight years of war and failed socialist policies.

"Three billion dollars would probably be inadequate in this place," said one envoy.