WASHINGTON (Reuters) - Anxious U.S. federal workers are expected to see another round of pink slips on Friday as President Donald Trump and top adviser Elon Musk pursue a wholesale downsizing of the government.

Thousands of workers at multiple government agencies have been fired so far this week, most of them recently hired employees still on probation at departments including Veterans Affairs, Education and the Small Business Administration. 

Officials from the Office of Personnel Management, which oversees federal hiring, met with agencies on Thursday, advising them to lay off their probationary employees, according to a person familiar with the matter.

About 280,000 employees out of the 2.3 million member civilian federal workforce were hired in the last two years, with most still on probation and easier to fire, according to government data.

Trump and Tesla CEO Musk's overhaul of the federal government appeared to be widening as Musk aides arrived for the first time on Thursday at the federal tax-collecting agency, the Internal Revenue Service, and U.S. embassies were told to prepare for staff cuts.

Trump says the federal government is too bloated and too much money is lost to waste and fraud. The federal government has some $36 trillion in debt and ran a $1.8 trillion deficit last year, and there is bipartisan agreement on the need for government reform.

His fellow Republicans who control majorities in both chambers of the U.S. Congress have broadly supported the moves, even as Democrats say Trump is encroaching on the legislature's constitutional authority over federal spending.

Critics have also questioned the blunt force approach of Musk, the world's richest person, who has amassed extraordinary influence in Trump's presidency. 

Firings at the Consumer Financial Protection Bureau, however, were going beyond probationary employees, sources said, with some employees on fixed-term contracts being axed. 

Trump and Musk have said they are committed to reducing the size of the federal bureaucracy, which they charge is unaccountable to the White House and blame for actively stalling Trump's policy initiatives.

They have already offered some federal workers an incentive package to quit voluntarily, tried to gut civil-service protections for career employees, frozen most of U.S foreign aid and have attempted to shutter some government agencies such as the U.S. Agency for International Development and the CFPB almost entirely.

About 75,000 workers have signed up for the buyout, the White House said. That is equal to 3% of the civilian workforce.

Unions representing federal workers have already sued to block the buyout plan and one of them, the American Federation of Government Workers, said on Thursday it will fight the mass firings of probationary employees.

"This is highly unusual to terminate all probationary employees and is being done in a highly unusual manner. We are reviewing all legal options," said J. Ward Morrow, assistant general counsel for the AFGE.

A suit filed on Thursday by the attorneys general of 14 states alleges Musk was illegally appointed by Trump and seeks an order barring him from taking any further government action.

Along with those court challenges, Musk and his Department of Government Efficiency, or DOGE, have been hit with several privacy lawsuits over their access to government computer systems. 

Two federal judges overseeing privacy cases against DOGE will consider on Friday whether Musk's team will have access to Treasury Department payment systems and potentially sensitive data at U.S. health, consumer protection and labor agencies.

Musk has sent DOGE members into at least 16 government agencies, where they have gained access to computer systems with sensitive personnel and financial information, and sent workers home.

DOGE did not respond to a request for comment on the widespread layoffs, but a spokesperson for OPM said the firings were in line with new government policy.