LOS ANGELES – About 20,000 AT&T Inc. workers in the Northeast and West went on strike Tuesday even as the telecommunications giant reached tentative deals with unions in the Southeast.

The company’s contracts with two major branches of the Communications Workers of America expired in early April, leading to months of acrimonious negotiations. Now, 17,000 wireline employees in California and Nevada and 3,000 employees in Connecticut have decided to strike, AT&T said in a statement.

The strike is especially “unfortunate,” AT&T said, considering that the company had just completed handshake agreements with other union workers over similar issues.