Negotiators for the coal industry and the United Mine Workers were reported to be close to agreement last night on a contract to end the nation's longest coal strike.

The accord approached as the strike - now in its 60th day - began to threaten energy supplies in Ohio and several Appalachian states, where power conservation measures are being ordered.

Yesterday's optimism about an imminet settlement was underscored when the UMW's 24-member bargaining council, composed of the union's top regional officers, was summoned to Washington - presumably to vote on a contract proposal. A union spokesman said the council was to gather on a "standby" basis this morning.

This does not mean that the strike, which has idled 160,000 UMW members and cut off half the nation's coal production since it started Dec. 6, will be over immediately.

The negotitators broke for dinner last evening, still reportedly short of an agreement on all details, and the talks have previously broken down just as things looked brightest.

Moreover, the bargaining council must approve any contract proposal before it is submitted to the union's working members for ratification. During the last contract negotiations three years ago, the council rejected the bargaining team's first proposal, sending UMW President Arnold Miller back to the bargaining table for more money before approving in somewhat sweetened contract later in the day.

Rank and file ratification would take 10 days or more, and both industry and union sources caution that apporval couldn't be taken for granted. The 1974 contract was approved by only a narrow margin in the coal fields, even though it contained one of the biggest union money gains - 54 percent over three years - in recent history.

Finally, it is expected that it could take 10 days to two weeks to return the coal fields to production, which means that utilities with little more than a month's supply of coal on hand could be nearing the bottom of their stockpiles by the time they start getting new coal.

One reason the union bargainers have held out so long has reportedly been to get a contract sufficiently generous to sell to a membership that has been forced to make hard sacrifices in order to sustain the strike, including cutoff of all medical benefits on Dec. 6 and termination of pension payments as ot two days ago.

Union negotiators earlier rejected an industry offer to increase wages and benefits by about 32 percent over the next three years, an offer characterized by the industry group as more generous than last year's settlement in the steel and communications industries.

The only major issue still left to be settled as of the resumption of intensive negotiations Wednesday afternoon was the size of the money package, including wages, which now average $7.80 an hour, exclusive of overtime, and certain fringe benefits.

Bargainers for the UMW and the Bituminous Coal Operators Associations, the industry group, earlier reached agreement on the other two major roadblocks to a settlement: the union's demand for guaranteed benefit payments and the industry's demand for protection against production losses caused by wildcat strikes.

Previous contracts linked industry benefit contributions to the volume of coal production, thus jeopardizing benefits when work stoppages reduced coal output. The new contract reportedly will provide for specified benefit levels, regardless of production volume.

A new labor stability clause would penalize miners responsible for wildcat strikes unless an arbitrator finds that employers' actions caused a work stoppage. An earlier UMW demand for a limited right to strike during a contract was dropped.

The current UMW strike officially became the longest in the union's history today. The previous record for a national strike was 59 days, set in 1946. A strike three years ago lasted three weeks.