Defense Secretary Caspar W. Weinberger defied Congress yesterday by refusing to recommend any cuts in his budget and urging members not to feel bound if the congressional budget resolution limits defense growth next year to 5 percent after inflation.

In a letter to Chairman John G. Tower (R-Tex.) of the Senate Armed Services Committee, Weinberger invited rebellion against the whole congressional budget process.

Tower had asked the secretary for help in keeping the forthcoming defense authorization bill to 5 percent real growth from fiscal 1983 to 1984 rather than the 10 percent President Reagan requested.

But Weinberger, possibly setting the stage for his biggest confrontation with Congress over military spending, said the growth rates the House and Senate Budget committees recommended to Congress should be regarded only "as a funding target. And as such the authorization and Appropriations committees are to be guided but not bound" by them.

The House version of the budget resolution called for 4 percent real growth, the Senate version 6 percent. Tower is assuming in marking up the bill authorizing money for military research and procurement in fiscal 1984 that the conferees will compromise on 5 percent.

But "if the House-Senate budget conference agrees on a 5 percent real growth defense funding level as stated in your letter," Weinberger wrote, "I will work diligently to persuade Congress that the president's budget, as modified, is essential to our national security and that any significant compromise thereto will jeopardize the president's ability to guarantee the security of the American people."

The secretary said that although "I appreciate the willingness of the committee to consider my recommendation" for cutting the Pentagon budget to keep it within a 5 percent growth rate, "neither the president nor I am prepared to recommend any reductions beyond those which could accrue from revised estimates of inflation and fuel costs" and from savings stemming from revising the MX missile deployment scheme.

Weinberger, in urging Tower to stand firm against any cuts, said the Reagan administration had to perform "double duty" because it had to make up for "years of neglect" by previous administrations in shoring up the nation's defenses while building for the future as well.

Cutting the growth rate from 10 percent after inflation to 5 percent would cost the Pentagon up to $14.7 billion in spending power, Weinberger said, and such a "wholesale budget authority reduction would cause serious damage to our commitment to rearm America, necessitating some reductions in the force structure, the readiness and sustainability of our combat forces and in our modernization programs."

Tower's letter to Weinberger came after the committee tried and failed in closed session Wednesday to find ways to reduce the budget. There was little support for dropping big weapons systems, sources said, which led members to turn to less glamorous accounts, such as manpower. One idea put forward, but not adopted, called for reducing the pay of freshly recruited soldiers--the E1 rank--by $150 a month.

Weinberger also refused to recommend budget cuts last year when asked by Sen. Ted Stevens (R-Alaska), chairman of the Senate Appropriations subcommittee on defense. Stevens lashed out at Weinberger then for his stubbornness.

The House, meanwhile, continued yesterday to debate its version of the procurement bill, defeating 319 to 73 an effort by Rep. Ronald V. Dellums (D-Calif.) to delete $432.8 million for Pershing II nuclear missiles, which are scheduled to be based in West Germany.

Dellums argued that deployment of the missiles, which could reach the Soviet Union, would be "dangerous and destabilizing" and would strain the western alliance. Deployment of the weapon, scheduled to begin in December, has produced deep political divisions in several western European countries.

After his Pershing proposal received one less vote than last year, Dellums decided not to introduce, at least now, proposals to shelve ground- and sea-launched cruise missiles.

"There seems to be a belief on the part of my liberal colleagues that they can only deal with one weapon at a time," Dellums said, referring to the MX missile that is scheduled to be debated in July. "They're afraid someone's going to label them as unilateralists."