A senior Republican in Congress who for years has advocated increased military spending yesterday called for major reductions in the Reagan defense budget and criticized the president's continued reliance on "mutually assured destruction" in a nuclear war.

"I'm scared to death of all this second-strike talk," said Rep. John J. Rhodes of Arizona, a former House minority leader. "The United States and the Soviets are playing poker with sticks of dynamite."

Reagan last week and again Monday asserted that the Soviets have the capability to launch a nuclear attack against the United States, absorb a U.S. retaliatory strike and then stage a second nuclear attack, and said this is proof of U.S. strategic inferiority. Many experts agree the Soviets have this capability, but say the United States does, too, and question whether it means either side is inferior.

In a speech prepared for delivery in the House after the Easter recess, Rhodes assailed both the military and the economic premises of the Reagan defense budget. The veteran congressman called for scrapping of the B1 bomber, a 70 percent reduction in MX missile expenditures, cutbacks in the Rapid Deployment Force and withdrawal of U.S. troops from Europe after consultation with members of the Atlantic alliance.

Rhodes' full-scale assault on the Reagan defense program was another important sign of the growing divisions among Republicans over the administration's approach to the arms race. Some Republicans are critical of particular weapons systems; others who largely support the military buildup nonetheless believe that Reagan is spending so much on defense that he is undermining his own economic recovery plan.

The most notable Republican critic has been former president Ford, who increasingly has urged cuts in military spending to reduce the growing federal budget deficit.

"I'm a hawk, I'm proud of it, and I don't intend to change," Ford told a Florida audience in February. "But I think there can be responsible delays in purchases of some big-ticket items in the defense budget."

Ford's favorite "big ticket" example that he says can be delayed has been the B1 bomber. Rhodes, previously a supporter of the B1, said yesterday that plans for the plane should be scrapped and the money spent on the advanced "Stealth" bomber advocated by the Carter administration. Reagan wants to build both.

The Rhodes speech systematically challenged the post-World War II premises of U.S. foreign policy and military planning based on the "needs and wants of Western Europe." The congressman criticized "lukewarm" support by European allies for U.S. efforts to free its hostages when they were held in Iran and said that European reactions to the Soviet invasion of Afghanistan and Russian pressure on Poland "have been measured, to put it mildly."

"We even see some of our allies actively aiding rebels in Central America against governments which have our backing," Rhodes said. "If 'linkage' is to be applied to our relations with the Soviet Union, and it should be, perhaps the same principle should apply to the actions, or lack of action, of our allies in various parts of the world."

Like his onetime partner in the House, Gerald Ford, Rhodes maintained that he is also still a "hawk" and a staunch anti-communist. But he said that U.S. policy had failed by simply reacting to the Soviets.

Rhodes, 65, acknowledged that his bold criticism of the Reagan administration's approach may have been influenced by the fact that he is retiring from Congress. In his speech, Rhodes cites the retirement warning of President Eisenhower about the dangers of the "military-industrial complex."

"Eisenhower was obviously right when he said that the military-industrial complex needed to be watched," Rhodes said. "It does. And it isn't being watched to the point that it must be in the future."