ATLANTA: As shippers across the country scrambled to find an alternative package delivery system, 185,000 United Parcel Service Teamsters walked off the job at on minute after midnight Monday morning after negotiators failed to agree on a new contract. The strike is expected to upset delivery service to thousands of businesses nationwide and will cost the company an estimated $50 million a day. Federal Express and the U.S. Postal Service have made contingency plans to take up the slack, but say they may have difficulty handling the additional load. Adding to the delivery giant's difficulties is a promise by 2,000 UPS pilots to join the strikers. And with President Clinton virtually ruling out federal intervention, it could be a long time before the dispute is settled. At issue for the Teamsters is limits on subcontracting and more full-time jobs. The company's desire to withdraw from the Teamsters' multi-employer pension and health funds is another key sticking point in the dispute. While the union has vowed to fight to the bitter end, the strike is certain to cost it dearly, with weekly expenditures reaching $10 million, much of it in the form of strike benefits.