NEW YORK (AP) — The labor contract with the largest union at Qwest Communications International Inc. expires today, little more than a week before the company is to provide phone and Internet service for the Democratic National Convention.

The Communications Workers of America has voted to authorize a strike, which could theoretically begin as soon as Sunday. The union organizes 20,000 Qwest workers in 13 states.

The same union was involved in contract negotiations with Verizon Communications Inc. recently. The parties were unable to reach an agreement before the expiration of the old contract, but workers stayed on the job for a week until a new deal was reached.

The Democratic convention starts Aug. 25 in Denver, Qwest's hometown.

"We remain hopeful that we'll see a tentative agreement this weekend," said Qwest spokesman Robert Toevs.

The company has extensive contingency plans in case of a strike and plans to maintain service across its network if one does occur, he said.

Qwest will also be providing telecommunications services for the Republican National Convention that begins Sept. 1 in St. Paul, Minn.