WASHINGTON — 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 Sen. Jeff Sessions for attorney general and Republican Rep. Mike Pompeo for director of the Central Intelligence Agency – are leading advocates for domestic government spying at levels not seen since after 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, including Apple Inc. and Alphabet Inc.’s Google. Trump signaled as much during his presidential campaign, when he urged a boycott of Apple for refusing to help the FBI hack into a terrorist’s encrypted iPhone.

An “already over-powerful surveillance state” is about to “be let loose on the American people,” said Daniel Schuman, policy director for Demand Progress, an internet and privacy advocacy group.

In a reversal of curbs imposed after Edward Snowden’s revelations in 2013 about mass data-gathering by the NSA, Trump and Congress may move to reinstate the collection of bulk telephone records, renew powers to collect the content of e-mails and other internet activity, ease restrictions on hacking into computers and let the FBI keep preliminary probes open longer.

A first challenge for privacy advocates comes this week: A new rule is set to go into effect on Dec. 1 letting the FBI get permission from a judge in a single jurisdiction to hack into multiple computers whose locations aren’t known.