Maintaining a freeze on North Korea's nuclear weapons program by providing heavy fuel oil to the communist country will probably cost the United States $50 million a year, double the amount expected, according to Clinton administration officials.

Other nations aren't contributing enough money for the 1994 program aimed at reducing nuclear tensions in a volatile region, the officials told a Senate Foreign Relations subcommittee Tuesday."Frankly, we were overly optimistic about our ability to attract funds from other countries and we have to be much more realistic now," said Rust Deming, deputy assistant secretary of state for East Asia. "We recognize that we are going to have to do more our-selves."

But even $50 million a year "is a small price to pay to reinforce peace on the Korean Peninsula and to strengthen the global non-proliferation regime," Deming said.

Members of the Senate panel, worried that Pyongyang will back out of the delicate 1994 deal, chastised the administration for not seeking increased funding sooner.

"To allow the agreement to languish in this way is the height of irresponsibility," complained Sen. John Kerry, D-Mass.

Sen. Craig Thomas, R-Wy., chairman of the East Asia subcommittee, said he was concerned because of indications North Korea might be looking for an excuse to back out of the agreement.

Pyongyang has recently done maintenance work on its closed nuclear plants. In May, a North Korean statement said the U.S. should meet its fuel oil obligations or "the consequences will be unpredictably serious."

"We also have to make sure that we don't allow North Korea to find reasons not to comply," Thomas said.

North Korea agreed in 1994 to shutter its plutonium-producing nuclear plants in exchange for a promise of free energy - in the form of heavy fuel oil to fire electric power plants now, they promise two light-water nuclear reactors to meet future electrical demands.

At the time, then-Secretary of State Warren Christopher said the U.S. contribution for heavy fuel oil would be $20 million to $30 million a year.

However, the cost to the United States already has jumped to $35 million annually, the program is $47 million in debt and deliveries are running months behind schedule.

By the end of July, 216,000 of 500,000 metric tons of heavy fuel oil due each year to North Korea will have been delivered, but there's no money to buy the rest by a mid-October deadline, Deming said.

While the total cost of the program is $65 million a year, other countries have contributed only $73 million since 1994, compared with $80 million so far from the United States, Deming explained.