The head of the nation's oil workers union today warned that "time is running out" on chances of averting a nationwide refinery strike next week, but pledged to continue bargaining until curret contracts expire at midnight Sunday.

A. F. Grospiron, president of the Oil, Chemical and Atomic Workers Union, told a news conference at the union's headquarters here that the oil companies have not budged from earlier offers that fall within the Carter administration's 7 percent anti-inflation guideline for wage and benefit increases this year.

He charged that the guidelines wrecked any chance of settling without a strike risk, and accused the oil companies of "hiding behind the voluntary Carter guidelines to deny their hourly employes sufficient wage and fringe benefit improvements."

The union has indicated that it will strike rather than settle for for a 7 percent increase, even though its ability to shut down the oil industry is hampered by the industry's extensive automation.

There had been speculation that Grospiron might signal the union's intention to strike today if he saw no possibility of reaching a negotiated settlement by Sunday.

Instead, he declined to speculate on the likelihood of a walkout by the OCAW's 60,000 oil workers.

"Time is running out," he said. "We may not be able to reach an agreement before our contracts expire, but we intend to keep trying. As of now, I do not intend to call for strike action. We are still bargaining, and a decision on possible strike action will be made at the time the contracts expire."

But union officials cautioned against over-optimism. "We can't be too optimistic right now," one said.

The union is in a weak position because refineries are so highly automated they can be operated by supervisory personnel for months, barring major breakdowns. Moreover, the industry, despite its relatively low labor costs, is under heavy pressure from the government to keep down wage increases because the oil industry bargaining constitutes the first test of the administration's 3-month-old anti-inflation guidelines.

The OCAW is calling for a "substantial across-the-board cents-per-hour wage increase" over the next two years, along with major improvements and fringe benefits, including company takeover of all health insurance costs. Grospiron has publicly set no percentage goal, but indicates that the union wants to match or exceed current cost-of-living increases, now running at more than 9 percent anually.

OCAW refinery workers now average $8.82 in straight hourly wages. They received increases of 9 percent a year during the current two-year contract.

Grospiron said today the negotiations are further complicated by some companies' insistence on exempting from any proposed wage increases newly hired workers and those currently working at entry-level jobs. He indicated this was unacceptable.

Grospiron contended that the companies are acting as though the union has "less clout than Master Charge," and took issue with claims that the industry is virtually strike-proof. He said there will be some decline in production because some refineries are already scheduling to close in the event of a strike.

While Grospiron virtually ruled out a formal contract extension after midnight Sunday, he indicated that there would be flexibility if progress were being made during the day toward a pattern agreement.

Bargaining is being conducted separately around the country for 411 individual contracts with as many as 100 oil companies, but a 12-member policy committee that has been meeting here since Thursday has the power to accept or reject any contract offer. Only Grospiron has the power to call a strike.