Lawmakers are facing a potentially bruising fight over a surveillance law that expires Dec. 31 and must be extended in time to preserve what U.S. spy agencies consider a vital piece of their arsenal.

Congress has to extend the 2012 FISA Amendments Act, which will pit the Trump administration and national security hawks in Congress who favor a permanent reauthorization with no changes, against lawmakers of both parties, libertarians, privacy advocates and communications companies seeking to tighten protections for U.S. persons whose communications may get caught up in the wide electronic net cast by spy agencies.

The U.S. intelligence community, led by Director of National Intelligence Dan Coats, has staked out its position: a permanent reauthorization of the law without any changes. A bill sponsored by Sen. Tom Cotton, R-Ark., would do just that.

The legislation has the backing of 13 Republican senators, including Intelligence Chairman Richard M. Burr of North Carolina, Armed Services Chairman John McCain of Arizona and Lindsey Graham of South Carolina, a strong voice on national security matters.

Coats and Thomas P. Bossert, White House advisor on homeland security and counterterrorism, have said the existing law defends the United States from terrorism, weapons proliferation and foreign espionage, and therefore should be made permanent without any changes.