President Reagan yesterday signed legislation providing $356 million to increase security at U.S. embassies worldwide and another $10 million to pay rewards for information about terrorist acts.

Two days before the presidential foreign-policy debate at which bombings of U.S. installations in Lebanon are expected to be a major topic, Reagan declared that the United States must "maintain a worldwide presence and not succumb to these cowardly attempts at intimidation."

"International terrorism is a growing problem for all of us in the western world, not just the United States," Reagan said in a written statement. He signed the bill without reporters present, but aides invited photographers into the Oval Office to record it.

The legislation provides rewards of as much as $500,000 for information about a planned terrorist act against Americans or U.S. property or for information leading to conviction of those who commit terrorist acts.

The administration initially sought $110 million for such security, saying it could not spend any more before January when it would seek additional funds as Congress reconvenes. Congress voted the larger amount, and Reagan said he is "grateful that the Congress responded swiftly . . . ."

The Sept. 20 bombing of the U.S. Embassy annex in Beirut killed two Americans and dozens of Lebanese and was the third such fatal attack against U.S. installations in Lebanon in about 17 months. Democratic presidential nominee Walter F. Mondale has charged that the administration ignored warnings about terrorist acts against U.S. facilities in Lebanon and failed to take protective action.

Reagan has recently attempted to deflect this criticism by pointing out, as he did yesterday, that "terrorist attacks are becoming increasingly violent and indiscriminate." Since Sept. 1, he said, "there have been 41 separate terrorist attacks by no fewer than 14 terrorist groups against the citizens and property of 21 nations."

Meanwhile, the wife of an American journalist kidnapped in Beirut last March said yesterday that a friend gave State Department officials a specific warning in August that a terrorist group was planning to attack a U.S. compound in Beirut between Sept. 20 and Sept. 22.

A State Department spokesman said yesterday that statements by Lucille (Sis) Levin, wife of Jerry Levin of Cable News Network, and George Malouf, a Washington-area architect who brought back the warning, did not change the department's position that it had received "no specific information" about the time, place or method of the bombing. He declined to elaborate.

The Washington Post reported earlier this week that U.S. and Israeli intelligence agencies received reliable reports in August that explosives targeted at Americans had been shipped into Beirut.

Levin is one of three Americans believed held captive by members of a group calling itself Hezballah. The Rev. Benjamin Weir, a Protestant minister, and U.S. Embassy officer William Buckley also have been missing for months. Levin said she and her friends believe that the three are being held in West Beirut.

Malouf told reporters yesterday that, while he was seeking news of Levin in Beirut, Hezballah leaders told him that part of the group was planning "to hit the United States . . . in a place where they don't think we can reach them" in the period between Sept. 20 and Sept. 22. Levin and Malouf said they took the information to officials of the State Department's counter-terrorism office in mid-August.

Levin said she decided to speak out now about her husband because she is concerned that the Reagan administration is considering "retaliation," rather than "reconciliation," in the Middle East. She said administration officials told her that chances of winning her husband's freedom are better if she remains silent.

Acknowledging that her public statement was motivated in part by the proximity of the presidential election, she said she wants Mondale to know that "thousands and thousands of people want peace and don't want to be looking at the Middle East over the barrel of a gun."

Describing the administration's Mideast diplomatic policies as a failure, she asked: "Why haven't these hostages been talked about? Why has it been left to stand that Reagan said there will never be hostages taken again? . . . . Why haven't you [the media] written about it? . . . . Are we bored with hostages? Is it now a ho-hum thing, or does America care anymore?"