In an apparent bid to ease strained trade relations with the United States, Prime Minister Zenko Suzuki today appointed a team of veteran political trouble-shooters to key Cabinet posts in the first major shakeup of his 16-month-old administration.

Amid a well-orchestrated public fanfare, the move was widely interpreted here as an attempt by Suzuki and his ruling Liberal Democrats to head off a potentially explosive conflict with Washington over Japan's mushrooming surplus on trade with the United States.

That surplus is expected to hit a record $15 billion this year and has prompted repeated warnings from Reagan administration officials that Japan should quickly redress the imbalance by opening its market to more American products or face a possible protectionist backlash in Congress.

But despite Suzuki's efforts to recast his Cabinet with more outwardly accommodating political heavyweights, it is believed that the maneuver will result in few, if any, substantial changes in Japan's lopsided trade advantage.

In today's most dramatic gesture, Suzuki bumped Foreign Minister Sunao Sonoda, replacing him with Yoshio Sakurauchi, a trusted political ally and a top leader of the Liberal Democrats.

In a series of statements in recent months, Sonoda has been sharply critical of American policy toward Japan. His replacement with the more soft-spoken Sakurauchi, political observers here said, is an attempt to "remove a source of needless provocation" from already delicate ties between the two countries.

In another key appointment, Suzuki named Shintaro Abe, who is widely considered a prime candidate for a future premiership, to head the powerful Ministry of International Trade and Industry.

After calling for the resignations of all 20 ministers in his Cabinet, Suzuki decided to reappoint chief Cabinet Secretary Kiichi Miyazawa, Finance Minister Michio Watanabe and Economic Planning Agency Director General Toshio Komoto to their former positions.

All five seasoned politicians have held important Cabinet portfolios or top executive posts in the ruling party and, in the unobtrusive style of Japanese politics, are regarded as "team players" in working toward a consensus on criticial issues.

In packing his Cabinet with such men, analysts said, Suzuki hopes to put an end to the intense rivalries that have hamstrung previous attempts to forge a policy to deal more effectively with the problems of Japan's chronic trade windfalls.

In announcing Cabinet appointments earlier today, Suzuki said, "we must make our utmost efforts to avoid a trade conflict with the U.S." He pledged his government's efforts to accelerate tariff reductions on a wide range of commodities and to streamline customs procedures that, foreign businessmen frequently charge, effectively keep their products from successfully competing in the Japanese market.

Despite Suzuki's apparent commitment to whittling down Japan's ballooning surpluses with both the United States and Western Europe, Cabinet officials remain at odds on whether Tokyo should attempt to turn the trick in the short run by boosting imports or clamping controls on exports.

Komoto, the new Economic Planning Agency chief, has given his strong endorsement to increasing spending on public works to help stimulate the domestic economy thereby creating, in theory at least, an expanded market for imports.

Finance Minister Watanabe, however, has publicly opposed economic pump-priming on the grounds that the appropriations would put an unacceptable burden on the country's already deficit-ridden finances. In statements to the press today, both ministers pledged to "coordinate" their views on the matter, but the bargaining between their competing departments is sure to intensify when the Cabinet enters into final deliberations on the 1982 budget next month.

The continuing conflict will, it is widely believed, delay action on an expected package of surplus-cutting measures until early next year.

"The Cabinet reshuffle," said one knowledgeable political analyst, "is designed to impress the Americans with Japan's good will in tackling the trade problem. But the changes are strictly cosmetic."