Michael Dukakis pledged Friday to double the number of federal drug agents over the next five years as he charged the Reagan administration with using a "nickel and dime" approach to the war on narcotics. George Bush ridiculed Dukakis' attempts to portray himself as a defense-minded candidate.

"You cannot fool the Soviet leadership by knocking America's defense for 10 years and then riding around in a tank for 10 minutes," the vice president said, referring to his Democratic rival's visit earlier in the week to a tank design facility in Michigan. "You can't fool the American people."Bush played tough in his television commercials, as well, airing an advertisement in Dukakis' home state of Massachusetts that accused him of failing to clean up polluted Boston Harbor.

The vice president headed for Washington after a three-city tour of Ohio, while Dukakis was flying home to Massachusetts on Saturday night. Both men have set aside large parts of next week to prepare for their first debate of the fall presidential campaign, a 90-minute nationally televised session a week from Sunday in Winston-Salem, N.C.

Democrat Dukakis has spent much of the week trying to regain the momentum in the race for the White House, and his tough anti-crime speech in a visit to the Los Angeles Police Academy was part of that effort.

In what has become the standard made-for-television element of every campaign day, he observed officer Jerry Mulford demonstrate "cover and concealment" tactics at a simulated street scene. Mulford ducked behind wooden boxes and a brick wall and fired at various moving and pop-up targets. Normally, live ammunition is used in such exercises, but the Secret Service protecting Dukakis vetoed that idea.

Dukakis said he would assign the first 100 new drug agents to Southern California. And he said he would double the total number of agents nationally over the next five years.

"We are going to give the state and local law enforcement officers the money they need to fight the war," he said. "We are not going to try to nickel and dime you to death, as this administration has done."

Aides said he was prepared to spend $50 million to hire new agents next year toward a five-year goal of 2,800 agents, although a fact sheet issued to reporters said the cost of the agents would be offset by seized drug profits.

Aides also said Dukakis was committed to hiring 800 additional federal prosecutors.

"We're going to send a message to drug kingpins," he said. "As far as Mike Dukakis is concerned, there's nowhere you can run; there's nowhere you can sail; there's nowhere you can hide; there will be no safe haven for dope peddlers and drug profits anywhere on this earth."

But while making an appearance at a Chula Vista, Calif., police station, Dukakis was greeted by pro-Bush demonstrators, some wearing striped mock prison uniforms and chanting, "Let me out, I'll kill again." The chant referred to the Massachusetts governor's furlough program, since modified, that enabled a convicted killer to go to another state and rape a woman.

Bush used his first news conference in two weeks to try and blunt some of the work Dukakis did earlier in the week to buttress his own defense credentials. He opened with a statement saying the tank Dukakis rode in "did not fit."

Later, he said, "He's gone to states like this, found that his message of cutting unilaterally on these weapons systems is not popular and so now he's been made over. He's coming out with policies quite different, but which ones do you believe?"

The vice president, who has moved up markedly in the polls in the last few weeks, acknowledged that some of his aides do not want him to take questions from reporters for fear it would distract from campaign themes he stresses in his other appearances. "It's just some lower-level hand-wringers who think I'm going to screw up," he said.