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Kevin Johnson, USA TODAY

WASHINGTON - National Security Agency Director Keith Alexander told a House committee Tuesday that 50 terror threats in 20 countries have been disrupted with the assistance of two secret surveillance programs that were recently disclosed by former defense contractor Edward Snowden.

At least 10 of the plots targeted the U.S. homeland, Alexander told the House Intelligence Committee, including a plot to bomb the New York Stock Exchange.

"I would much rather be here today debating this,'' Alexander told lawmakers, referring to the programs' value, "than explaining why we were unable to prevent another 9/11'' attack.

At the rare open committee hearing, Alexander and Deputy Attorney General Jim Cole told lawmakers that both surveillance operations-a domestic telephone tracking system that collects records of millions of Americans and an Internet monitoring program targeting non-citizens outside the U.S.-said programs have been subject to rigorous oversight to guard against privacy abuses.