SAN FRANCISCO (AP) _ A new city law aimed at protecting workers who use video display terminals faces a string of amendments that would give businesses more time to comply.

The law, which affects city workers and private businesses with 15 or more employees, requires adjustable workstations, regular breaks and training on safe use of VDTs. It also recommends transfer to non-VDT work for pregnant women who ask to be moved.

''This legislation ... will ensure San Francisco workers are protected from dangerous injury, without driving away businesses,'' said Mayor Art Agnos, who signed the bill Thursday. ''It's legislation on the cutting edge of social change.''

The ordinance requires compliance within two years for most businesses. But after Mayor Art Agnos met last weekend with business and labor leaders, amendments were proposed for a compromise plan that will be voted on next month by the Board of Supervisors.

The proposed changes are a three-step program for compliance:

-After one year, new equipment would have to meet standards in the ordinance.

-For existing workstations, retrofitting that costs less than $250 would have to be completed within 30 months.

-Retrofitting that costs more than $250 would have to be completed within four years.

The compromise was reached after business and labor officials said they found the time constraints of the ordinance unacceptable.

''We hope that careful administration of this ordinance provides something we all can live with,'' said Gwen Kaplan, president of the San Francisco Small Business Association. ''At best, it's a first step toward long-range solutions.''

The legislation was pushed by a coalition of activists who cited dangers to VDT operators, including repetitive strain injury, back and neck pain, deteriorating vision and possible miscarriages.

''This is the beginning. We had to have a beginning,'' Paul Varacalli, executive director of Service Employees International Union Local 590, which backed the bill, said after the signing.

The ordinance will be enforced by the city's health department, which will hold public hearings on compliance, said Agnos spokesman Art Silverman.

On Wednesday, Supervisor Tom Hsieh, who opposed the measure, said it violated city charter. He said a section of the charter states supervisors can't change working conditions for city employees without studies by the Civil Service Commission.

But Jonathan Holtzman, special assistant in the city attorney's office, said the section cited applies only to changes in compensation, not safety measures, and that the ordinance is legal.

Supervisor Angela Alioto, a co-author of the ordinance, said it was drafted ''to make it challenge-proof in court.''

''I don't think there's any possible challenge that could knock this down,'' she said. ''We attempted to make this one constitutional, and I believe it holds up.''

The law will affect an estimated 56,000 workers and will cost about $14 million in the private sector within the first 30 months, Varacalli said.

It will cost an estimated $231,552 to bring the city into compliance, he said. Agnos said he'd like to upgrade city equipment as soon as possible and that the cost is built into the city's budget.