President Reagan defended his Latin American policies here today, arguing that support for governments with poor human rights records and paramilitary leaders is necessary if the United States is not to be "paralyzed with indecision."

He said the security of the Western Hemisphere "rests as much on American willpower as firepower."

Reagan's remarks came in a fund-raising speech for Sen. John G. Tower (R-Tex.), who is expected to face a tough reelection fight next year.

Reagan aides said the speech was intended to build public support and pressure on Congress for support of U.S. actions to aid friendly governments in Latin America. One said the president was seeking to bring America's policy "out of the dark" by explaining why U.S. intervention in Latin America should not be perceived as an embarrassment and "something to be done in covert operations."

On Thursday, House Majority Leader James C. Wright Jr. (D-Tex.), an ex-officio member of the House Permanent Select Committee on Intelligence, said he thought congressional support could be gained for an increase in U.S military aid to El Salvador by legislating a replacement of covert action with "overt" assistance.

Reagan's effort comes as the Intelligence Committee appears ready to establish a prohibition on covert U.S. actions in Nicaragua. However, the committee delayed its vote earlier this week and may support some additional overt U.S. action to aid of the government of El Salvador.

The president wants financial support for the U.S. intervention to remain at current levels of about $30 million a year or to increase as the committee approves overt U.S. activities in the region.

The president was delayed 10 minutes on his way into the city when two Houston motorcycle policemen collided and Reagan stepped out of his limousine to comfort one who was injured. Reagan told the policeman, identified as Sgt. Ralph Gonzales, "I'm sorry this happened," before the officer was taken to the hospital and later released.

Speaking in a state that he said was "closer to El Salvador than it is to Massachusetts," Reagan said at the fund-raiser that any consideration of withholding U.S. aid from Latin American governments because of questions about human rights violations and other problems would allow Soviet influence to overwhelm America's southern neighbors.

"There are those who suggest that because our friends in Central America are not perfect we must back away and permit those armed to the teeth by the Soviets to do as they will, to shoot their way into power," Reagan said. "The only alternative the American people have been presented is a 'prescription for disaster.' "

The president said that the United States alone possesses the power to counter Soviet aggression and therefore "remains the last, best hope for a mankind plagued with tyranny and deprivation."

Tower, chairman of the Senate Armed Services Committee, has been one of Reagan's staunchest supporters on Capitol Hill. Although he has been in the Senate 22 years, Tower has been identified by the National Republican Senatorial Committee as one of the party's most vulnerable incumbents next year.

Tonight's fund-raiser, featuring the president, was expected to raise over $1 million for a Tower reelection campaign that may cost more than $5 million.

Tower is the most prominent Republican in this state, which is a key to Reagan and the party in the 1984 presidential election. The party suffered a severe setback in the 1982 elections in which Democrat Mark White scored a surprising upset of Republican Gov. Bill Clements.

Reagan touched on politics only briefly in his speech, taking a shot at former vice president Walter F. Mondale, who is the front-running candidate for the 1984 Democratic nomination.

"You remember," Reagan said, recalling the nation's economic problems when he was elected in 1980, "they called it a malaise. And now former vice president Malaise is running for president, promising he can do everything just like they did before."

In his speech, Reagan reminded his audience that the challenge of communism in Central America is "not some threat in a distant land, it is a brush fire burning in our own neighborhood."