At the U.S. State Department, the dissent began building soon after President Donald Trump signed an executive order late on Friday to limit immigration from seven Muslim-majority countries.

Opposition mounted through the weekend as a draft memo criticizing Trump's policy was written up in Washington and circulated by email to U.S. diplomatic posts around the world, according to multiple officials involved in the effort.

By Monday, two of the officials said they considered withdrawing their names from the document, fearing a backlash.

On Tuesday, just 12 days into Trump's presidency, the memo with some 900 signatures was delivered to the State Department policy planning office and from there to other top officials, said one source familiar with the document.

Sources said this was an unprecedented number of names on a memo sent through the department's formal "dissent channel."

The memo is just one example of the alarm and, in some cases, resistance spreading within the federal bureaucracy as Trump's administration makes sharp policy turns while ignoring some of the agencies charged with implementation, according to interviews with more than 20 current and former U.S. officials who spoke on condition of anonymity and in some cases asked that their departments not be identified.

Still fearful of recriminations, one official said some diplomats discussed whether they could qualify for professional liability insurance, which would cover legal costs in the case of disciplinary action, through the American Foreign Service Association union.

The White House did not respond to an email requesting comment.

Earlier, when the existence of the memo surfaced, White House spokesman Sean Spicer warned that anyone at the State Department who questioned Trump's immigration policies "should either get with the program, or they can go."