WASHINGTON (AP) — A Senate Intelligence Committee Democrat on Monday blocked a five-year extension of a surveillance law used by the Obama administration to intercept the communications of terrorist suspects overseas.

The move is the latest by Sen. Ron Wyden of Oregon to address concerns that the government may be reviewing the emails and phone calls of law-abiding Americans in the U.S. who are at the other end of communications being monitored abroad.

A year ago, Wyden and Sen. Mark Udall of Colorado asked the administration for an estimate of the number of people in the U.S. whose communications were reviewed by the government under the law, the Foreign Intelligence Surveillance Act Amendments of 2008.

The office of the Director of National Intelligence responded that it was “not reasonably possible to identify the number of people located in the United States whose communications may have been reviewed.”

In a letter Monday to Senate Majority Leader Harry Reid of Nevada, Wyden said he will object to any request to pass the current version of the bill with unanimous consent, that is, without a vote. Wyden said he will work with colleagues in an effort to amend the bill.

The 2008 legislation was designed to give the government new authority to collect communications of people believed to be suspected terrorists who are foreigners outside the U.S. The legislation was supposed to preserve the privacy of people inside the U.S. on the other end of the communications.

Wyden says the government should be barred from searching through these communications to find phone calls or emails of a particular American who might have been picked up as an unintended by-product of other authorized surveillance, unless the government obtains a warrant or emergency authorization.

Wyden and Udall offered an amendment during intelligence committee consideration of the bill to prohibit such searches for Americans’ communications. It was defeated.