WASHINGTON – In a Cold War-era dispute that is worthy of fiction, two former Soviet Bloc defectors are asking the Supreme Court for the right to sue the American government for reneging on a secret spy deal.

The defectors, known only as Mr. and Mrs. Doe, accuse the agency of reneging on what they say was a promise by the Central Intelligence Agency to take care of them for the rest of their lives, in exchange for espionage services decades ago.

In oral arguments today, the agency’s lawyers will ask the justices to dismiss the case on the grounds that any litigation would require the government to acknowledge the existence of a secret agreement. It has long been established that the government may deny any relationship if the arrangement is exposed or suspected, government lawyers argue.

“Secrecy in all aspects of the CIA’s espionage activities is necessary in order to protect the lives of the spies as well as the CIA employees who recruit them,” states the government’s written brief to the court in the case known as Tenet v. Doe.

But a district court and the U.S. Court of Appeals for the 9th Circuit have said the Does case should be allowed to proceed and that a judge may permit the agency to withhold certain information on national security grounds.

Lawyers for the agency will today ask the justices to overturn that ruling and to keep such cases out of the courts. They add that the government cannot sue spies for failing to carry out their covert activities.

“The relationship is both entirely secret and entirely outside the law, and its terms are not specifically enforceable through legal means by either side,” the government argues.

In documents before the court, the Does tell a story of manipulation and exploitation by the agency and claim that their constitutional rights have been violated.

Mr. Doe, who worked as a senior diplomat in a Soviet bloc country before deciding to defect, claims that he had no interest in becoming an American spy. Disenchanted with communism, he approached a U.S. Embassy and was taken away to an agency safehouse, where he was held long enough to make it impossible to return to his old job safely.

The Does claim they were pressured by the agency into undertaking espionage that would virtually guarantee that their activities would become known to their home nation, putting them at lifelong risk of retaliation, including assassination.

“Believing they had no choice, the Does complied with the CIA’s demands for progressively more dangerous activities,” their lawyers state in a written brief to the court.

The Does claim they fulfilled their part of the bargain and relocated to America. But when Mr. Doe lost his job at a Seattle bank in 1997, the agency declined to help him, citing budget constraints. The Does allege they tried various appeals to the agency and were given various answers for why they had been cut off.

They argue that their freedom and physical well-being are threatened if they return to their homeland.

The government says their case is a contract dispute that cannot be enforced in court. Its argument relies on a Supreme Court ruling in an 1875 case called Totten v. United States, in which the court said a Civil War spy could not sue Abraham Lincoln for breaching an agreement because the agreement itself had to remain secret.

Lawyers for the Does counter that they are not seeking to enforce a contract, but rather to compel the CIA to provide a procedurally fair internal agency hearing for their claims for assistance and personal security, and a declaration that the CIA is required to comply with substantive law in dealing with their claims.

Lawyers for the Does argue that the government’s position will hurt America’s ability to engage foreign agents in the war on terrorism.

Depending on how the court rules, the case could open or shut the federal courthouse door to claims not only by informants and double agents but also by agency employees, said a lawyer who represents the people suing the agency, Mark Zaid.

“When they join the FBI and CIA, they know there will be limitations, but all of those restrictions are lawful,” Mr. Zaid said. “But if their agency conducts itself in an unlawful manner, if it discriminates racially or gender-wise, or retaliates against a whistleblower, the government should not be able to turn around and claim national security to protect its unlawful conduct.”