Hundreds of janitors demanding a wage increase and better health benefits walked off their jobs at some of Silicon Valley’s largest high technology companies Tuesday in a strike that organizers said will continue through the week.

The janitors went on strike after contract discussions ended last Thursday between the Services Employees International Union – which represents 6,000 janitors – and the Bay Area Maintenance Contractors, representing 15 contractors who provide janitorial services to local companies.

“The strike is for me, my co-workers, for life and respect,” said Elsa Guich, 62, one of about 100 janitors who walked off at Cisco’s North San Jose offices early Tuesday. “The company doesn’t understand that we work hard. They need to understand.”

Many Bay Area companies like Cisco and Hewlett-Packard hire contractors who employ janitors like Guich to clean their buildings. A master contract with 15 companies represented by Bay Area Maintenance Contractors expired April 30. After labor talks ended last Thursday, the union rejected what was described as the contractors’ “final offer.”

Janitors at Cisco, HP, Oracle, Yahoo and eight other work sites went on strike. Officials with Cisco and HP said the strike has not affected their operations.

In striking, SEIU is attempting to make its case directly with the companies, as it bids for higher wages and improved health benefits. But the companies seem to be resisting that effort.

“This is a contract dispute between our supplier, SBM, and the union,” said HP spokesman Ryan Donovan. “We hope for a rapid resolution between the two parties.”

Guich, an immigrant from Peru, has worked for GCA Services cleaning at Cisco for eight years. She makes about $11 an hour, about $2 less than her counterparts in Los Angeles, and $7 less than San Francisco janitors, according to the SEIU.

The cleaning contractors offered an average of 40 cents an hour increase, said Mike Garcia, SEIU president. The union also is seeking to eliminate a requirement that new employees wait two and half years before they can obtain health benefits for family members.

“The janitors feel like they’re being short changed,” Garcia said. What the cleaning contractors offered, he said, “does not remedy the reality of life for many workers. They felt insulted and rejected.”

Jim Beard, chief negotiator for the cleaning contractors, said he offered SEIU a 50 cent hourly wage increase for the first year of a four-year contract. Declining to give specifics, he said contractors offered a 20 percent overall increase – combining wages and benefits – for the four-year period.

“It’s disappointing that this is happening,” said Beard. “And we’re disappointed they want more.”