The Central Intelligence Agency and its oversight sentinels in Congress took the first major steps last week to prevent former U.S. intelligence agents from supporting international terrorism through the sale of expertise, explosives and armaments.

CIA officials disclosed to key members of Congress that agency lawyers have been redrafting the basic employment contract for clandestine agents and technical specialists to include prohibitions against the sale of their trade crafts to hostile foreign governments or terrorist organizations.

Meanwhile, in the Senate, a member of the Intelligence Committee, Lloyd M. Bentsen (D-Tex.), introduced a bill closing a loophole in the federal criminal code that previously had left the government powerless to prosecute Americans who go overseas to help terrorists.

In addition, the chairman of the House Intelligence Committee, Rep. Edward P. Boland (D-Mass.) announced that his committee will conduct comprehensive investigative hearings on the activities of the most notorious of the ex-CIA operatives, Edwin P. Wilson, who has provided extensive aid, technology and materiel to radical Libyan dictator Col. Muammar Qaddafi.

Wilson and his one-time business partner, Francis E. Terpil, also an ex-CIA agent, were indicted by a D.C. federal grand jury in April, 1980, for various alleged violations stemming from their shipments of high explosives, delay-action timers, sensitive night-vision equipment and commando training programs to Libya. Both Wilson and Terpil are fugitives.

Following the initial allegations against the two ex-agents in September, 1976, federal prosecutors encountered a number of legal hurdles in preparing their criminal case, which includes a charge that Wilson and Terpil attempted to execute a $1 million assassination contract against a Qaddafi critic living in Egypt.

The CIA employment contract, whose stringent conditions for secrecy have ensnarled several former agents' attempts to chronicle their experiences in and criticisms of the agency, is being redrawn in utmost secrecy because of its potential impact on thousands of current intelligence employes and any future careers in private business. It is known to include a review of whether the agency can cut off retirement benefits of those ex-agents who violate the terms of the contract. The rewrite may also attempt to forbid covert agents from going to work for the governments of foreign countries where they were stationed as U.S. agents.

On Capitol Hill, Bentsen's international terrorism crime act of 1981 would prohibit the sale of weaponry, explosive devices, munitions, plans and other war materiel to foreign agents or governments for the purpose of aiding or abetting international terrorism.