The FBI, National Security Agency and CIA are likely to gain expanded surveillance powers under President-elect Donald Trump and a Republican-controlled Congress, a prospect that has privacy advocates and some lawmakers trying to mobilize opposition.

Trump's first two choices to head law enforcement and intelligence agencies -- Republican Senator Jeff Sessions for attorney general and Republican Representative Mike Pompeo for director of the Central Intelligence Agency -- are leading advocates for domestic government spying at levels not seen since the aftermath of the Sept. 11, 2001, terrorist attacks.

The fights expected to play out in the coming months -- in Senate confirmation hearings and through executive action, legislation and litigation -- also will set up an early test of Trump's relationship with Silicon Valley giants including Apple Inc. and Alphabet Inc.'s Google. Trump signaled as much during his presidential campaign, when he urged a consumerboycott of Apple for refusing to help the FBI hack into a terrorist's encrypted iPhone.