On the eve of his Geneva summit, President Reagan stands near the peak of his personal popularity, enjoys the highest ratings of his presidency in handling relations with the Soviet Union and has eased considerably fears that his military policies have increased the chance of nuclear war, according to a new Washington Post-ABC News poll.

Reagan's improved ratings on foreign policy come as he has both taken dramatic action against international terrorists and moderated his often hard-line rhetoric against the Soviet Union in the period leading to his summit meeting with Soviet leader Mikhail Gorbachev.

The poll showed that 67 percent of those surveyed approve of the way Reagan is handling his job. The only time his approval ratings were noticeably higher -- at 73 percent -- was immediately after the assassination attempt against him in the spring of 1981.

Once seen as a president who resisted arms control efforts and was unwilling to talk to the Soviets, Reagan is now viewed by 84 percent of those surveyed as someone who "seriously wants to make progress in arms control."

At the same time, Gorbachev enjoys a positive rating among the American public. Of those surveyed, 44 percent said they have a favorable opinion of Gorbachev compared to 38 percent who do not. Fifty-six percent said he is seriously committed to making progress on arms control.

Nonetheless, the public is sharply divided on the question of whether Reagan and Gorbachev will be able to achieve such progress in Geneva, although by 58 percent to 38 percent, they said the summit will ease tensions in the world.

As the United States and the Soviet Union have exchanged proposals to sharply reduce offensive nuclear weapons, however, the public has grown more optimistic about the prospects for significant accomplishments at the summit. Roughly three-quarters of those surveyed said they want the two nations to make such reductions, even though about the same percentage expects the Soviets to cheat on any agreement that is negotiated.

The survey shows the public divided over the merits of Reagan's Strategic Defense Initiative (SDI), which is expected to be a key issue at the summit, although by a ratio of better than 3 to 1, they prefer a reduction in offensive arms to the development of space weapons.

Those surveyed appear convinced that the president's costly military buildup has closed the gap in U.S.-Soviet military power and decreased the chances of a nuclear confrontation.

In the national telephone poll of 1,507 people contacted from last Sunday through Wednesday, Reagan scored impressive approval ratings on a variety of questions.

On foreign affairs generally, 61 percent approved of Reagan's performance, about the same as the four-year high of 62 percent registered in a late October poll.

Sixty-four percent approved of his handling of relations with the Soviet Union, matching the record-high rating of last month.

In apparent support of his more conciliatory approach to the Kremlin, the president's approval rating has steadily risen since he announced April 1 that he had invited Gorbachev to a summit.

Although nearly half of those questioned said the president has previously failed to work as hard as he should have for arms control, the 84 percent who now consider his efforts serious crosses gender, regional and party lines.

As further recognition of Reagan's less confrontational stance, people who said they believe his policies have increased the chance of nuclear war dropped from 31 percent in April 1983 to 18 percent in the current poll, while 37 percent said they believe his policies have decreased the prospect of nuclear confrontation, compared to 15 percent in 1983.

On the question of Reagan's trillion-dollar defense buildup, 54 percent said they believe the nation is stronger militarily since he took office, 37 percent said they see little change and only 6 percent said they feel it is weaker.

More people said they believe U.S. military power is superior to the Soviet Union -- 24 percent -- than at any time since the question was first asked in 1979.

Twenty-six percent said the Soviets are stronger and 46 percent said they see rough parity.

A majority of those surveyed said the increased military strength has helped to make the world safer, with 54 percent saying the buildup has decreased the chances of world war.

Seventy-three percent said they think a U.S.-Soviet nuclear war in the next few years is "unlikely" -- the highest number since April 1982 -- and 26 percent said they believe it is "likely" -- the lowest number since the issue was first polled.

The poll produced differing views on Reagan's controversial space-based missile defense, popularly known as "Star Wars." Gorbachev wants to block development of SDI as the condition for limiting nuclear arms, while Reagan steadfastly has defended his vision of a nuclear shield that he says would make nuclear war obsolete.

Although a small majority favored SDI, 71 percent of those polled said it is "more important" for the United States to agree to a "substantial reduction" of nuclear weapons than to build a nuclear defense umbrella.

The poll showed that 55 percent of Americans -- up from 48 percent in October -- support a system that would "guarantee protection" of the nation against nuclear attack regardless of cost. Thirty-eight percent -- down from 46 percent last month -- oppose the system, agreeing with the statement that it would escalate the arms race and cost many billions of dollars to build.

A closer look at the poll's findings indicates the highly politicized nature of SDI, which appears to be more of a litmus test of support for Reagan than a technological issue.

Among those who compose the small majority of supporters, 66 percent are Republicans, 65 percent voted for Reagan in 1984, 63 percent approve of his overall handling of the presidency and 64 percent consider themselves ideologically conservative.

Of SDI opponents, 48 percent are Democrats, 52 percent voted for Walter F. Mondale in the 1984 presidential election, 30 percent approve of Reagan's handling of the presidency and 47 percent consider themselves liberal.