WASHINGTON (Reuters) -The White House is scrutinizing layoff plans by federal agencies in an effort to limit further court challenges after the Supreme Court cleared the way for a sweeping downsizing of the government workforce, according to two senior White House officials with knowledge of the matter.

The White House Counsel's Office and the Office of Personnel Management are coordinating with federal agencies to ensure their plans comply with the law, one of the officials said. That includes meeting requirements set by Congress, such as rules for how layoffs must occur and the minimum number of staff an agency must retain.

The official declined to give a specific timetable for when layoffs will begin but said the plan is to move quickly.

"The goal is to simplify the size of the federal government, so we will do what we need to do to reach that goal," the official said, calling the downsizing an "immediate priority."

The Supreme Court's decision on Tuesday opened the door for President Donald Trump's administration to pursue thousands of government job cuts across multiple agencies. While administration officials have called the effort a streamlining of government, unions and their allies warn the layoffs will disrupt lives and essential services, and hollow out agencies already stretched thin.

The White House on Tuesday had applauded the Supreme Court ruling but stopped short of saying agencies could immediately execute the workforce reduction plans they drafted at Trump's direction earlier this year.

With hundreds of thousands of unionized federal workers, large-scale layoffs must also comply with labor contracts or risk additional legal challenges. 

Legal experts say that even if the administration meets basic legal thresholds, agencies may still face broader lawsuits related to due process, civil service protections, union rights and public access to services.

One of the senior officials said the administration expects legal challenges.

"You're just going to see in the coming days, the different plans that sort of come out ... they're going to be legally sound, (but) they're still gonna get lawsuits, because that's just the way it goes," the official said.

On Thursday, the U.S. State Department said it was moving forward with its plan to lay off employees. The department is widely expected to send the first notices of employment termination on Friday. In late May, the agency had proposed laying off nearly 2,000 employees.

Upon taking office in January, Trump launched a campaign to downsize the 2.3 million-strong federal civilian workforce, an effort led by billionaire Elon Musk and his Department of Government Efficiency.

By late April, the project had resulted in the firing, resignations and early retirements of 260,000 federal employees, according to a Reuters tally.

The U.S. departments of Agriculture, Commerce, Health and Human Services, State, Treasury, Veterans Affairs and more than a dozen other agencies submitted layoff plans to the White House in March to reduce staff. Months of legal uncertainty have left those plans stuck in limbo until this week's ruling.