By Daniel Wiessner

Dec 4 (Reuters) - A judge on Thursday blocked the U.S. State Department from immediately laying off more than 250 workers, a legal setback for President Donald Trump and his mass firings of government employees.

U.S. District Judge Susan Illston in San Francisco said employee unions that filed the lawsuit were likely to prevail on their claim that the planned cuts, which include civil service and U.S. Foreign Service positions, are not allowed under a law Congress passed last month to end a 43-day government shutdown.

The layoffs were set to take effect Friday. Illston's order is temporary and does not address the merits of the case.

The law, known as a continuing resolution, prohibits agencies from implementing layoffs through January 30. The Trump administration has told agencies that the law does not apply to job cuts that had been announced before the shutdown began on October 1, including more than 1,300 State Department layoffs that were first announced in July. Hundreds of those workers were terminated in September, before the shutdown.

The American Federation of Government Employees and American Foreign Service Association said in Wednesday's filing that the administration's interpretation of the law is wrong. They asked Illston to issue a ruling by Friday morning blocking the layoffs, pending further litigation.

Morale within the Foreign Service, the U.S. diplomatic corps, is tanking. A recent survey conducted by the American Foreign Service Association showed 98% of the 2,000 respondents reported poor morale while 86% said changes in the workplace since Trump took office in January have undermined their ability to implement foreign policy. Only 1% reported improvement.

The State Department did not immediately respond to a request for comment.

The filing was made in a lawsuit the unions brought in October to block several federal agencies including the State Department from laying off more than 4,000 employees during the government shutdown.

Illston sided with the unions, ruling that implementing layoffs was not an essential government service that can continue during a shutdown. In May, Illston in a separate case brought by federal worker unions temporarily blocked the government from laying off thousands of employees, a key piece of Trump's plan to shrink and reorganize U.S. agencies.

The U.S. Supreme Court paused that ruling in July, but the administration scaled back planned layoffs after tens of thousands of employees accepted buyouts or retired early.

(Reporting by Daniel Wiessner in Albany, New York, Humeyra Pamuk in Washington, D.C. and Jack Queen in New York; Editing by Alexia Garamfalvi, David Gregorio and Lincoln Feast.)

Reuters

US judge blocks 250 State Department layoffs for now