The nation’s top intelligence official insisted on Wednesday that he did not lie to Congress about powers of the National Security Agency nearly three years ago.

James Clapper, the director of national intelligence, has repeatedly battled allegations over his 2013 claim that the U.S. does “not wittingly” collect data on millions of Americans. Leaks from Edward Snowden just a few months later showed that, in fact, the NSA collected bulk records about millions of phone calls in the U.S. 

{mosads}“[Y]es, I made a mistake,” Clapper said in a conversation on the intelligence office’s Tumblr account on Wednesday. “But I did not lie. There’s a big difference.”

Clapper and his aides have offered subtly varying explanations for the apparent mischaracterization that all hinge on the idea that he was thinking of a separate NSA program and not the collection of phone data.

Shortly after details of the NSA program were revealed in 2013, Clapper said that his response was the “least untruthful” answer possible. 

“When someone says ‘collection’ to me, that has a specific meaning, which may have a different meaning to him,” he said then.

Last year, a top lawyer for Clapper explained the slip-up by claiming that the spy chief “had absolutely forgotten about” the existence of the phone program and was instead thinking about the agency’s collection of people’s behavior on the Internet. 

On Wednesday, he offered a similar explanation.

“When Senator [Ron] Wyden [D-Ore.] asked me the question I simply didn’t think of the [phone records program], at the time stored by NSA and governed by Section 215 of the Patriot Act,” Clapper wrote. “Instead, I thought of content — given his reference to ‘dossiers’ — which, in my mind, meant Section 702 of the Foreign Intelligence Surveillance Act which governs collection on non-U.S. persons overseas.

“We were in an unclassified hearing, and I thought we were talking about an unclassified program,” Clapper added, noting that the phone records program was classified at the time.

The post helps to clarify an issue that has dogged Clapper’s tenure, though it is unlikely to appease Clapper’s critics. Some of those, such as Sen. Rand Paul (R-Ky.), have said he ought to resign over the issue.

Following Clapper’s claim on Wednesday, Wyden noted that he had given the question to the spy head in advance, and that Clapper had also “refused” to correct the record afterwards.

Clapper’s office has claimed that only staffers had an opportunity to preview Wyden’s questions ahead of time — not the spy chief himself. He chose not to publicly amend the comments, general counsel Robert Litt claimed in 2014, because of their classified nature.

Section 702 of the Foreign Intelligence Surveillance Act authorizes the NSA’s sweeping PRISM and Upstream collection programs, which target foreigners but may incidentally also pick up the content of Americans’ communications. Privacy advocates have pushed for a change to the law, which comes up for renewal at the end of next year. 

The NSA was forced to end its bulk collection of phone records last year after a heated battle in Congress. 

This story was updated at 6:07 p.m.