Embattled negotiators for Chrysler Corp. and the striking United Auto Workers held a marathon bargaining session lasting more than 37 hours and appeared headed last night toward a settlement or a complete breakdown in the effort to end the seven-day strike by 70,000 workers in 15 states.

"We have reached the make-or-break point," a UAW official at the Detroit talks said late yesterday. "It may work out tonight or it may unravel completely. We're at the point where each side is saying, 'Either you move on this or we are finished,' and you never know how it's going to end."

Chrysler Chairman Lee A. Iacocca, who has not participated directly in most of the bargaining sessions, spent several hours at the bargaining table until 2 a.m. yesterday and met with UAW President Owen Bieber to try to fashion a compromise.

Negotiations resumed at 9 a.m. Monday -- as Canadian UAW members were ratifying a separate pact with Chrysler -- and stretched through the night and into yesterday in a dozen rooms at Chrysler headquarters in Detroit.

UAW officials issued a statement at midday saying that "we took some important steps in the right direction" but adding that "several major items" were unresolved. The UAW said talks would continue as long as there was hope of progress. The company had no comment.

UAW sources said complicated issues involving job-security guarantees, profit-sharing formulas and duration of the new contract were among the key unresolved matters.

The week-old strike is costing the nation's No. 3 auto maker an estimated $10 million a day as the company loses daily production of more than 1,500 vehicles, according to industry analysts.

The strike has also led to many layoffs in the 8,000 automotive supply firms that provide up to 70 percent of Chrysler components. Analysts estimate that more than 150,000 people work for U.S. firms that supply Chrysler parts and could be subject to layoffs in a protracted strike.

Chrysler's six Canadian plants resumed most operations yesterday following approval of the new 23-month contract by the 10,000-member Chrysler division of the Canadian UAW. But company officials have said they could be forced to lay off most of the Canadian work force by next week if the U.S. strike continues. Auto plants on both sides of the border depend on each other for parts.

The UAW's key demand has been that Chrysler, now achieving record profits after a brush with bankruptcy, agree to match the terms of UAW contracts with General Motors Corp. and Ford Motor Co. This would require Chrysler to increase its $13.23 average hourly pay by about 2 percent to 3 percent annually, with larger increases in pension payments. The UAW also would require the company to begin a profit-sharing plan and to provide funds for job-security programs to retrain and relocate workers in the event of layoffs.

Company officials have said that despite the firm's $3.5 billion profit in an 18-month period, its continued recovery depends on controlling labor costs because Chrysler's reliance on smaller cars makes it more vulnerable to Japanese competition than is either of its larger American competitors.

In addition to parity with GM and Ford, which the Canadian UAW won in its agreement, the American union is seeking what Bieber called "something special" to compensate Chrysler workers for the $1.1 billion in wage and benefit concessions they made between 1980 and 1982 to help the company recover. Canadian workers will receive a $1,000 bonus as partial compensation for past concessions.

The length of the contract is a major issue to both sides. Chrysler wants the stability of a standard three-year contract, but the UAW wants a 23-month pact that would return the company to the 30-year tradition of "pattern bargaining," in which the Big Three auto contracts expire simultaneously. That allows the union to pick a single strike target, negotiate a contract and then threaten to strike the competitors if they refuse to accept the settlement.