A Federal Reserve Board survey of senior bank loan officers indicated yesterday that banks are tightening credit for American businesses of all sizes.

In the survey of 78 banks, 43 percent reported more stringent standards for general business loans to mid-size companies, and more than one-third said their standards were tighter for both large and small companies.

Lending for commercial real estate was also off: Compared with six months ago, three-quarters said they had tightened loan standards for construction and land development, and 60 percent for mortgages on office buildings.

"The results ... suggest that the weakness in growth of commercial and industrial loans this year {is attributable} in some part to a reduced willingness on the part of banks to lend," the survey said.

The most important reasons loan officers gave for tightening standards on business loans other than real estate were "a less favorable economic outlook and industry-specific problems," the survey said. Loan officers also cited a deterioration of their loan portfolios and pressure from regulators.

The survey did not say why lenders had tightened real estate credit. Many real estate lenders and borrowers have attributed the so-called credit crunch to pressure on banks from financial regulators.

In mid-July, Fed Chairman Alan Greenspan told the Senate Banking Committee that banks appeared to be lending less to U.S. businesses. The latest survey confirms his testimony and data from other sources.

The survey blamed the crunch on more conservative banking practices in the aftermath of the savings and loan crisis, the general slowing of the domestic economy after years of strong growth and problems in specific industries.

"Domestic respondent banks indicated that since May they have further tightened lending standards and terms" on business loans not tied to mergers and acquisitions, the Fed said. "The tighter stance was particularly noticeable for lending to middle-market firms but was significant for larger and smaller firms as well," the survey indicated.

"Branches and agencies of foreign banks reported that, on balance, they too have moved to restrict the availability of business credit," the Fed said.

No changes were reported in the willingness of financial institutions to lend money to U.S. households through credit cards and other consumer instruments, but the survey found less "enthusiasm" for home-equity loans. "This apparent relative de-emphasis on home-equity lending ... may be attributable to a number of factors, including some recent slowing in the appreciation of home prices and increases in delinquency rates on home-equity lines of credit," the survey said.