U.S. Businesses Plan 5.1% Rise in Investment : Economy: The increase in spending on plants and equipment is seen by some as another sign of sluggishness.

American businesses plan to boost spending on plants and equipment 5.1% this year, the lowest increase in three years, the government said today in a report reflecting economic sluggishness even before the Persian Gulf crisis began.

The Commerce Department said a survey conducted in July and August found businesses planned to spend $526.9 billion for expansion and modernization this year, the fourth consecutive year of increased business investment.

Although the survey was still under way at the time of the Aug. 2 Iraqi invasion of Kuwait, some analysts said the spending plans were little affected by the crisis.

“It is unlikely that the Kuwait situation would have much impact, given that most of this spending is already set in motion,” economists at Mitsubishi Bank in New York wrote in their current newsletter.

If realized, the investment spending would top the record $501.6 billion in capital expenditures set last year.

But the 5.1% rate of increase was the lowest since a 3.1% gain in 1987 and less than half the 10.4% advance last year. Capital spending rose 9.5% in 1988.

The new estimate also is down from the 5.5% spending increase that businesses said they planned in the previous survey, completed in May.

Many analysts have been looking for continued business investment to help stimulate an economy that has been slowing for more than a year as the Federal Reserve kept a tight rein on credit to curb inflation.