Army General Keith Alexander, testifying with other US spy chiefs before the House of Representatives Intelligence committee, tried to defuse a growing contro-versy over reports of NSA snooping on the citizens and leaders of major US allies.
The hearing took place as Congress is considering legislative proposals that could limit some of the NSA's more expansive electronic intelligence collection programs.
Mr Alexander said: "It is much more important for this country that we defend this nation and take the beatings than it is to give up a programme that would result in this nation being attacked."
On Monday, that criticism broadened to include Senator Dianne Feinstein, chairman of the Senate's intelligence panel and long-time ally of US spy agencies.
The White House has moved to limit some NSA programmes, including one that monitored the mobile phone of German Chancellor Angela Merkel, and Presi-dent Barack Obama has also curtailed NSA monitoring of the UN head-quarters in New York.
Mr Alexander said reports of NSA spying in Europe, based on documents leaked by former NSA contractor Edward Snowden, were exaggerated.