The Senate voted overwhelmingly Friday to order the U.S. military to enter the war against illegal drug trafficking, approving a plan to give the Navy the power to stop drug boats on the high seas and make arrests.

The chamber voted 83-6 approval of an amendment outlining a wide-ranging anti-drug plan for the military.The proposal provides more surveillance by Air Force and Navy planes, a bigger anti-drug role for the National Guard and more Pentagon helicopters for the Coast Guard and Customs Service.

The most controversial provision would require Navy vessels to track suspected drug boats in international waters and would allow Navy officers to arrest suspected drug traffickers. The officers would be temporarily "deputized" by Coast Guard officers who would be aboard for that purpose.

The anti-drug provision was the main unresolved issue as the Senate worked toward approval of a bill authorizing defense spending for the fiscal year starting Oct. 1.

Passage by the Democratic-controlled chamber will send the bill to a House-Senate conference committee to reconcile differences between it and the separate Pentagon bill approved Wednesday by the House. Both measures authorize $299.5 billion for the Pentagon.

One major difference will be the anti-drug provision. The House measure orders President Reagan to have the military "substantially halt" the flow of illegal drugs into the United States.

"I think we have a chemical war being directed against the United States," said Sen. Sam Nunn, D-Ga., chairman of the Armed Services Committee.

But he warned that the military help won't solve the problem. "Let no one believe that we're going to pass a piece of legislation and solve the drug problem, but we can improve it. I think we all know the drug epidemic in this country is far past the stage where interdiction can stop it."

Other senators warned that drugs have become a national security menace, but they also acknowledged that the military plan won't solve the problem.

The loudest critic was Sen. John Glenn, D-Ohio, who accused his colleagues of "posturing on this."

"We all get up, posture, make our little statements, and it isn't going to make any difference," said Glenn, arguing that the U.S. lacks a coordinated or effective nationwide anti-drug program.

"It's absolutely ludicrous to think this will solve the problem," he said.

The Pentagon has resisted a larger role in the war against drugs, saying the military is not trained or equipped for the assignment.