The poll, which tracks the Bank of Japan quarterly business survey, yielded a manufacturers' business sentiment index of plus 9 in April, recovering from minus 1 in March.

For the three months ahead, however, the index was seen falling back to zero.

A positive figure indicates optimistic respondents outnumber those who are pessimistic about their business outlook.

The poll was conducted over April 2-11, just as U.S. President Donald Trump introduced a 25% tariff on car and truck imports and a further 24% tariff on Japanese goods - though the latter has been cut to 10% for 90 days.

The outlook turned sour particularly among export-heavy businesses such as automotive and machinery makers.

"With uncertainty increasing around Trump's tariffs and other global affairs, we've seen a slump in orders since late February and there are a number of other worrying factors ahead," a manager at a precision machinery maker wrote in the survey on condition of anonymity.

"It's absolutely impossible to predict the impact of Trump's tariffs," wrote a manager in the automotive sector.

Another manager at a machinery maker said clients have been cautious about investing due to tariff uncertainty.

Some also cited weakness in China's economy as a source of concern.

"Weak demand in China has caused low-priced products to flow into the Japanese market," a chemicals firm manager wrote.

Of 505 major, non-financial companies surveyed, 222 responded.

The poll's service-sector business sentiment index rose to plus 30 in April from plus 25 in March, while the index was seen at plus 21 in the three months ahead.

Real estate and information service firms were confident about their outlook whereas shipping firms voiced concern about rising labour costs and falling volume due to intensifying Sino-U.S. trade tension.