NEW BEDFORD, Mass. (AP) _ Talks to end the 20-day-old fishermens' strike tying up this rich fishing port will not resume before Friday, says an attorney for fishing boat owners who broke off bargaining without explanation.

''We had some communications difficulties,'' attorney David Barnet said late Tuesday, after vessel operators stalked out of contract negotiations. ''It was just not appropriate to continue any further.''

He said he expected no meetings with the fishermen until after he met Thursday night with his clients.

''I'm sure there will be other sessions,'' said Barnet. ''None is scheduled.''

An hour after talks began on Tuesday, the negotiators of the Seafood Producers Association, representing the owners, asked striking members of the Seafarers International Union to leave the room so they could caucus, said Jack Caffey, vice president of the union.

''We were standing outside, standing by waiting to be called in, and all we saw was a mass exodus going out of the room,'' Caffey said. ''They didn't say one word.''

Federal mediator Austin Skinner said he was disappointed, but would try to get the parties together again.

Earlier in the day, union members had expressed optimism that the strike might be close to resolution.

Boat owners agreed on Monday to let union accountants review their financial records. Union port agent Joseph Piva said relations between the fishermen and boat owners were ''a little less hostile.''

New Bedford fishermen went on strike Dec. 27 in a dispute with boat owners on how to divide profits from the catch and other issues. The walkout has tied up this major seaport south of Boston, the most profitable port in the nation in 1984.

About 30 boats carrying non-union crews have left port since the strike began. The union represents crews on about a third of the 250-boat fleet.

The strike is costing about $146,000 a week in unemployment benefits alone, according to state mediator John J. Mark.

Although New Bedford was the top port in the nation two years ago in the value of fish landings - $107.7 million on 99.5 million pounds of fish - boat owners say skyrocketing insurance and maintenance costs and record poor catches are cutting deeply into their profits.

The union wants to keep the status quo on the crew's share: 64 percent on scallopers with crews paying expenses, 58 percent on draggers with owners and crew sharing expenses, or 59 percent with crew paying expenses.

The boat owners propose changing the scalloper crew share to 53 percent, with the crew paying expenses. On draggers the owners offer two options: 51 percent to crews which share costs of fuel, food and ice, or 53 percent with crews carrying all expenses.

The owners also propose giving captains absolute right to hire and fire; the union seeks a grievance procedure to contest what it believes are unjustified firings.