The U.S. Department of Justice has asked a federal judge to block a threatened flight attendants strike against Northwest Airlines, saying a work stoppage would cause serious disruptions to the air transportation system.

In a filing late Wednesday with the U.S. District Court, the government said a strike also would violate the federal Railway Labor Act, which requires that both sides of an airline labor dispute be released from mediation before workers can take job action.

The Association of Flight Attendants has threatened to strike as early as Friday if the bankrupt airline does not negotiate a contract for the workers.

"Because Northwest and AFA remain bound by the provisions of the RLA, they must continue to negotiate as required by law," the government said. "The AFA is therefore not entitled to strike at this time."

The AFA contends that its right to strike was triggered last month when Northwest terminated its members' contract and imposed new terms that grant the airline $195 million in annual labor savings. Northwest had bankruptcy court permission to impose new terms.

The AFA said it may stage surprise intermittent strikes on Friday, a move Northwest says could force its liquidation. Bankruptcy Judge Allan Gropper last week declined to block the strike, saying the matter was out of his jurisdiction.

Northwest has appealed to a district court, and a hearing is set for Friday, just hours before the 10:01 p.m. EDT strike deadline.

Separately, the airline said in a government filing Thursday that it had entered into a credit agreement with lenders led by Citicorp USA. Lenders will make term loans to Northwest amounting to $1.05 billion and revolving credit loans of up to $175 million.

Northwest said it borrowed all amounts available to pay off Northwest's second amended and restated credit agreement dated April 15, 2005. The airline said it would use remaining proceeds from the financing for working capital and other general corporate purposes.