Secretary of State Alexander Haig and U.S. Trade Ambassador William Brock yesterday delivered a strong warning to Japan's new Minister of Trade that time is growing short for Japan to take positive steps to reduce its hefty trade surplus with the United States. Brock said the surplus will reach $20 billion this year.

Brock, Haig and other American officials yesterday sought to impress on Shintaro Abe that U.S. trade deficits with Japan in the $15 to $20 billion range are "politically unsustainable."

In a 20-minute meeting at the White House, Abe delivered a message to President Reagan from Japanese Prime Minister Zenko Suzuki pledging an intensified effort to reduce "trade frictions" between the U.S. and Japan, which Suzuki said "is the most important external task that has to be dealt with" by Japan."

The American effort is directed primarly at encouraging Japan to expand its imports, rather than cutting off its exports here, although Brock hinted the U.S. may be getting ready to ask Japan to send fewer than the l.68 million cars allowed here in 1982 under the current "voluntary" quota.

Figures released yesterday in Tokyo by the Finance Ministry put Japan's 1981 trade surplus with the U.S. at $13.4 billion, almost double the $7 billion surplus of 1980. Japanese data on trade, on a customs-clearance basis, vary from American statistics. As calculated by Brock, the Japanese surplus was $10 billion in 1980, about $19 billion last year and will be at least $20 billion in 1982, with not much relief in sight for 1983 or 1984.

At the State Department, Haig told Abe that there is only a limited period of time in which Japan can take credible actions to reduce the trade surplus.

Haig also pressed Abe--to the official's surprise--to renew now-suspended talks on aviation routes. Japan has resisted an American proposal that United Airlines be allowed to fly into Tokyo, insisting that air traffic between the two countries is already unfavorably balanced against the Japanese side.

Reagan expressed his "appreciation" to Abe for Suzuki's promise to cope with the trade problem. Japanese sources said that Reagan was also pleased by two other points in the Suzuki message--a pledge of support for the American position on Poland, and a reiteration of the Japanese intention to boost defense expenditures.

Abe reiterated yesterday that Japan at the end of the month would make a "drastic" cut-back in so-called "non-tariff barriers" that American and European officials claim artificially choke off imports into the Japanese market.

But Brock said at a press conference yesterday more than this would be needed to solve world trading problems that had "reached very serious proportions". He was talking not only about bilateral U.S.--Japanese trade problems, but contentious trade and investment issues that sour relationships between the U.S. and Canada, and between the U.S. and the Common Market.

"Very concrete actions have to be taken over the next several months to avoid a regression into protectionist policies," Brock said.

The most critical U.S.-Japan issue now relates to Japan's successful penetration of the passenger car and truck market, despite "voluntary" quotas designed to provide a breather for the U.S. industry. Any change in current quotas for this year must be made prior to April 1.

But in the next few years, the problem is likely to focus on Japanese penetration of computer and other high technology markets.