Japan's world trade surplus, the source of repeated conflicts with the United States and other foreign countries, is tapering off dramatically this year and may wind up amounting to only about one-third of last year's surplus.

Trade figures made public this week show that Japan actually ran a sizable deficit of $453 million in its current accounts balance in April, a modern record and the second consecutive monthly deficit.

Both Japanese and American analysts speculated today that Japan may end this year with a current account surplus of about $5 billion or $6 billion compared to a worldwide surplus of more than $16 billion last year.

If the trend continues-and officials expect it to do so for several months at least-Japan will have resolved its most pressing problem with the world, the one which has made it the butt of international criticism for the past several years.

U.S. officials said today they believe the trade turnaround already has taken much of the heat off of Japan as the seven-nation economic summit here approaches, although European countries are still critical.

One American official described the recent trend as representing a "major shift" in Japan's position in the world. He declined to speculate on how long the trend would last, but a colleague said, "We have several good months coming."

The newest evidence shows a considerable increase in Japanese imports of American goods, a fact which could have an impact on the congressional debate on trade issues. Some congressmen have advocated an import surcharge on Japanese goods and complained that Japanese resistance to American imports justified a toughening of protectionist restrictions.

Japan has feared a protectionist retaliation by the U.S. for more than a year, and Prime Minister Masayoshi Ohira's recent state visit to Washington was a major effort to head it off. Japanese officials also have said they were concerned that anger with this country's surpluses would become an important issue in the American presidential election next year and have pointed with alarm to the anti-Japan theme in the speeches of former Texas governor John Connally, a Republican aspirant.

However, it now appears likely that Japan's large trade surplus with the United States will be considerably reduced this year. Officials speculate it probably will amount to between $7 billion and $8 billion, compared with a $11.6 billion surplus last year.

Moreover, one of the few remaining major trade arguments between the U.S. and Japan - the one involving Japanese government procurements - seems likely to be resolved this weekend when Special Trade Representative Robert Strauss arrives.

Strauss and Japanese officials are expected to negotiate a final agreement opening up government purchases to foreign bidders. The main sticking point has been the refusal of Nippon Telegraph and Telephone to permit foreign bids on some of its sophisticated equipment. Ohira said yesterday the issue will be settled Saturday.

The new trade figures show a dramatic change in the first four months of this year, ending with a total current account deficit of about $100 million. In the same period last year, Japan ran a $6.8 billion surplus with the world.

The main reason for the change was a large increase in imports coming into Japan. Imports from around the world have been running about one third higher than in the early months of 1978.

A major long-run reason for the turnaround, officials said, is that the change in currency exchange rates is now being felt in trade. The Japanese yen has appreciated by about one third in the past two years, making it cheaper to import foreign goods.

Statistics released by the U.S. embassy showed very sizable increases last year in Japanese imports of American office machinery and computers, electrical machinery, and applicances, and telecommunications equipment. Japanese imports of all kinds of American machinery and transportation equipment increased by 50 percent in 1978.

U.S. officials also said that the unexpectedly strong revival of the Japanese economy late last year contributed heavily to the surge of imports, because it opened Japanese consumers' pocketbooks to foreign goods.

"This is the second biggest economy in the world now and when it takes off it draws in imports from all over the world," one official said.

Japanese exports to the United States have continued to increase in dollar terms this year but not at the rapid rates chalked up in previous years and when measured by volume many key exports have actually declined.