WASHINGTON (Reuters) – A bipartisan group of at least 10 U.S. senators plans to introduce on Tuesday legislation that would substantially reform aspects of the National Security Agency’s warrantless internet surveillance program, according to congressional aides.

The effort, led by Democrat Ron Wyden and Republican Rand Paul, would require a warrant for queries of data belonging to any American collected under the program. The bill’s introduction is likely to add uncertainty to how Congress will renew a controversial portion of a spying law due to expire on Dec. 31.

Section 702 of the Foreign Intelligence Surveillance Act is considered by U.S. intelligence officials to be among their most vital tools used to combat national and cyber security threats and help protect American allies.

It allows U.S. intelligence agencies to eavesdrop on and store vast amounts of digital communications from foreign suspects living outside the United States.

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