The Teamsters union and the trucking industry continued intense bargaining yesterday, facing a midnight Sunday deadline on a nationwide contract covering 200,000 truckers whose worries about job security have risen along with their employers' concerns about surviving on the highly competitive highways.

Both sides said yesterday that the likelihood of a nationwide strike was slim, but union and industry sources said two Midwest management groups were resisting contract terms deemed acceptable by the 35 largest carriers, which are represented by a third bargaining group, Trucking Management Inc.

The union and TMI issued a joint statement yesterday saying they "expect to successfully conclude talks" by the deadline, but an industry source said "some serious problems" remain with the Motor Carrier Labor Advisory Council Regional Carriers Inc., which represents hundreds of smaller firms.

Wages and benefits were the final items being negotiated yesterday following weeks of haggling over the two most troublesome items. One was the job loss caused by dozens of organized companies setting up nonunion subsidiaries and using subcontractors. The other was the companies' proposal to set up a "two-tier" wage scale in which new employes would earn substantially less than the $13.26 hourly average of the National Master Freight Agreement.

These issues present a major challenge to Teamsters President Jackie Presser, who has never conducted national trucking bargaining before and whose last initiative in trucking was overwhelmingly rejected by his membership. Presser, under pressure from struggling companies, proposed a concessionary agreement including a two-tier pay system in 1983, but truckers rejected it by an 85 percent vote.

Union sources said yesterday that negotiators led by Presser were prepared to accept a lower starting pay rate if the new hires eventually progressed to the normal pay scale and if it was accompanied by a substantial pay raise for veteran truckers, who have not had a raise since 1982. Pension benefits also have been frozen for six years in most Teamster funds.

Negotiators said they will continue meeting and issue a statement Sunday evening.

Deregulation of the trucking industry has decimated the ranks of the union and the employers since 1980, as more than 10,000 new nonunion operators have hit the nation's roads. More than 100,000 Teamsters have lost jobs, and hundreds of firms with total revenue of more than $3 billion have gone bankrupt or closed as nonunion firms and railroads have taken away substantial business.

"Double-breasting" -- setting up a nonunion firm to take away Teamsters' work -- is supposed to be prohibited by contract, union officials said, but firms have skirted the contract by using holding companies.

Past protests have failed to slow the trend, as major freight firms have recently bought or started at least 15 nonunion companies. Roadway Express, one of the biggest union firms, has launched nonunion Roadway Package System, which is to compete nationwide with United Parcel Service, a Teamster-represented firm.

The current national contract covers fewer drivers than ever in the 21 years since the late Teamster president Jimmy Hoffa initiated a master agreement in 1964 as a means of consolidating union bargaining power. Since deregulation, growing numbers of firms are insisting on terms different from those in the master agreement.