The United Mine Workers and coal operators have reached an agreement to avoid a threatened second round of cuts in miners' benefits so long as miners don't go back on strike before their contract expires in December.

The agreement - announced yesterday by the UMW, the Bituminous Coal Operators Association and the funds' independent trustees - does not meet militant miners' demands for restoration of the July benefit cuts that sparked a 10-week wave of wildcat strikes this summer in the Appalachian coalfields.

But, in carrot-and-stick fashion, it guarantees no further cuts so long as the miners stay on the job. It also signals abandonment of earlier union demands for immediate restoration of the July cuts and threats of a nationwide coal strike if full benefits weren't restored by mid-October.

Making no mention of the union's earlier demands, UMW President Arnold Miller said the union will "insist" on full restoration, plus expansion, of previously won benefits in the new contract.

In the meantime, he said, any more strikes will mean more cuts. "If there is a new wave of wildcat strikes," said Miller, "it will be impossible for us to maintain the benefits we announced this morning" - meaning the July benefit level under which miners are liable for up to $500 of their annual health costs, instead of receiving free care, as before.

Earlier this month, the funds' trustees announced that impending strike-caused defi its in health and pension funds might force a reduction in benefits, including pension payments, in October. This sparked fears that a new cutback would cause a new wave of strikes, thus further reducing the production royalties that support the benefit funds.

Under yesterday's agreement, income from two health funds - one with a surplus, one with a deficit - would be pooled so that both would be solvent. This pooling does not contemplate reallocation of pension funds, which the BCOA has refused to allow. A spokesman for the trustees said the health funds pooling would be sufficient to cover medical payments through expiration of the contract, assuming no strikes.

The agreement also provides that the trustees shall obtain loans, estimated at about $8 million for October alone, to cover expected pension fund shortages until the contract expires.

The wildcat strikes, which during the summer idled as many as 85,000 miners, about half the UMW's working membership, have now virtually ended, with only a few thousand miners still striking, according to the BCOA.

The pension and benefit funds are still felling the effects of the strikes, however, because the funds' payments come from production levels achieved two months earlier. October payments are based on production in August, when the strikes were at their peak.