The U.S. Postal Service announced an emergency contingency plan yesterday to ration shipments of packages if rival United Parcel Service goes on strike next week.

The emergency plan could be implemented as early as Saturday or Sunday, strike or no strike, if shippers begin to inundate the post office with parcels, however.

"We are already beginning to see surges of volume," said Deputy Postmaster General Michael S. Coughlin. "There is no way the Postal Service can absorb the operations of the United Parcel Service overnight or even in a relatively short period of time . . . we do not have the capacity," he said.

"We want to protect the 500 million pieces of mail we are already moving," he added.

United Parcel Service's contracts with the Teamsters union expire July 31, and Teamster members are voting on a three-year contract offer. "For the most part they're not talking the word strike," said Ron Carey of New York, president of the largest Teamster local at United Parcel Service. If the contract is rejected, he said he expected the union to stay on the job while negotiations continued.

Although the union leadership has urged members to reject the contract offer, its basic wage and benefits appeal to a large number of workers, a union source said. The company adjusted its offer so permanent employees would get a boost in benefits and part-time workers -- many of them college students -- would get an up-front bonus when the contract was signed.

The company has offered a 50-cents-an-hour increase at the start of each contract year and 35-cents-an-hour each year for benefit increases. The typical worker is paid $16 per hour.

United Parcel Service delivers 10 million packages a day by truck across the nation, 20 times more packages than the Postal Service.

Coughlin said the Postal Service will meet with trucking representatives today and has alerted the Labor Department and the White House about its contingency plans.

The use of the military to deliver mail has been "given some consideration, but we have a capable work force, and there is not a lot the military could do in the very short run," he said. Mailers would be limited to four parcels under the emergency plan. Larger shippers would call a toll-free number and be assigned a time and place to deposit packages for home or business delivery. Under its plan, the Postal Service intends to require large shippers to arrange their own city-to-city or cross-country hauling.

For example, Coughlin said, a Washington business that wanted to ship 500 packages to Los Angeles would be given a time period to deliver its packages to the Los Angeles bulk mail center for delivery in the city and surrounding suburbs.

Coughlin said if there is a surge in the more expensive priority mail category, it "probably will have the effect of slowing it down by about a day."