United Mine Workers leaders, in some contract negotiating saber-rattling, warned yesterday that a national coal strike is inevitable by Dec. 6 unless virtually non-stop talks begin immediately.

Negotiations were started last Thursday but suspended until today by mutual agreement, with even some union officials conceding that they were not fully prepared for the talks last week.

Responding to the call for "continuous bargaining" from UMW President Arnold Miller, a spokesman for the Bituminous Coal Operators Association, the industry bargaining group, said it "stands ready to negotiate in good faith." A BCOA source indicated the mine operators would be willing to talk so long as there was something substantive to talk about.

A nationwide coal strike when the current UMW-BCOA conrac expires Dec. 6 has been widely anticipated for months. Although Miller said yesterday at a press briefing that a strike could still be averted, he outlined serveral positions that could provoke one - principally the union's demand for a right to strike over local contractural grievances.

Under this demand, which Miller characterized as "absolutely essential," UMW locals could, by majority vote of their members, strike over contract disputes that are now largely settled by arbitration. Such a strike could spread to other mines but only by majority vote of each local unit.

Miller said this would head off the kind of unauthorized wildcat strikes that idled up to 80,000 Appalachian coalminers last summer and help store "labor relations at the mine site." He predicted that most miners would be willing to strike only over a "serious contract violation" by the employers.

BCOA, however, has rejected any right-to-strike clause, proposing instead that disciplinary action such as withholding of benefits to strikers be considered as a method of controlling wildcat walkouts.

Miller said he doubted the union which ratifies contracts by rank-and-file vote would accept a contract without the right to strike but refused to rule out the possibility. He said he was not "particularly inclined" to recommend such a contract.

Miller also said the union wants "guaranteed" funding for health and pension benefits, which are now financed by royalties that rise and fall with coal production. Production declines forced benefit cutbacks that triggered last summer's wildcat strikes. The UMW is demanding full restoration of the lost benefits, along with guarantees of no further losses.

Miller conceded the benefit funds could "go under" in a protracted national strike but emphasized that a strike can still be averted. Some observers have speculated that the precarious state of the benefit funds may force the union to settle without a strike.

The UMW has not yet proposed a wage package and would say only that it will involve "substantial" increases. UMW miners currently earn about $65 a day and proposed $100 a day at their convention last year.