ASHINGTON, April 21 The White House has not asked Congress for the money that the Energy Department needs to harden nuclear weapons plants against terrorist attack, a high-ranking Energy Department official complained in a letter to the Office of Management and Budget.

The Energy Department's budget for security and safeguards, meaning protection against theft of nuclear material or information, is "not sufficient to implement the security posture requirements that appropriately respond to the September 11th attacks," the letter said.

Representative Edward J. Markey, a Massachusetts Democrat who has long been critical of nuclear security arrangements, plans to release the letter on Monday.

The letter, dated March 28, was sent by Bruce M. Carnes, director of the Energy Department's Office of Management, Budget and Evaluation, to Marcus Peacock, an associate program director at the Office of Management and Budget, a White House agency.

Mr. Carnes wrote that he had been told that the department's request had been turned down because the government was still rewriting the "design basis threat," the document that describes how many attackers the plants must be prepared to repulse and what information and equipment they will have available.

"This isn't a tenable position for you to take, in my view," Mr. Carnes wrote. "We are not operating, and cannot operate, under the pre-September 11 Design Basis Threat. Until that is revised, we must operate under Interim Implementing Guidance, and you have not provided resources to enable us to do so."

Mr. Markey said he feared that terrorists could break into a weapons plant and use conventional explosives to disperse radioactive material, or even assemble a nuclear bomb and explode it.

One of the plants is in the San Francisco Bay area and another is in a Denver suburb.

"The administration has requested almost $8 billion for missile defense, which won't do anything to prevent suicidal terrorists from attacking nuclear facilities and blowing up dirty bombs or homemade nuclear weapons," he said in a statement. "But when the Department of Energy finally admits that security is not what it should be, the Office of Management and Budget refuses to help."

A spokeswoman for the Energy Department, Lisa Cutler, asked about the letter, said on Friday: "The weapons complex is among the most secure facilities in the world, and would present a very formidable challenge to any terrorist organization.

"We took immediate steps in the week of Sept. 11 to improve site security and define our priorities for long-term improvement."

Ms. Cutler said a first request for a budget supplement had been approved, allowing the department to meet its highest priorities.

"If we find we need additional funds to meet our security needs this year, we'll make funds available to meet those needs," she said.

The department could do that by redirecting money, or by having the White House ask Congress for an additional appropriation, she said.

"We are going to meet our security needs, period," Ms. Cutler said.