Wray is expected to cite threats from Iran and China to argue that the sweeping surveillance powers authorized under Section 702 of the Foreign Intelligence Surveillance Act, which is set to expire at the end of this month, are vital to U.S. national security.

"Stripping the FBI of its 702 authorities would be a form of unilateral disarmament," Wray will tell the Democratic-led Senate Judiciary Committee during an oversight hearing, according to excerpts of his testimony released by the FBI.

The surveillance power of the U.S. government has come under scrutiny from U.S. lawmakers on both the right and left in recent years, particularly the ability of federal law enforcement to search for data on U.S. citizens picked up as part of surveillance of foreign targets.

A bipartisan team of U.S. lawmakers introduced legislation last month to impose new limits on searches of Americans' communications and prohibit so-called "backdoor" searches which invoke foreign intelligence justifications to spy on Americans.

U.S. officials have opposed new warrant requirements, arguing that information collected under the law has been vital to countering cyber threats and thwarting foreign intelligence operations directed against the United States.

Wray plans to tell the Senate panel that the FBI will be "good stewards of our authorities," citing reforms he said the FBI has already made in response to criticism of law enforcement's use of the law.

Wray, an appointee of former President Donald Trump, will appear before the Senate Judiciary Committee after facing a range of attacks from congressional Republicans on issues including the investigation into the Jan. 6, 2021 attack on the U.S. Capitol, the probe of President Joe Biden's son Hunter and claims the FBI pressed social media companies to censor conservatives.

(Reporting by Andrew Goudsward; Editing by Don Durfee and Kim Coghill)

By Andrew Goudsward