Julian Assange, the founder of WikiLeaks, on Sunday declined to say whether Russia was connected to the cache of damaging Democratic National Committee emails his group released before the start of the party’s convention.

Assange cited confidentiality of sources, telling NBC’s “Meet the Press” that revealing who hacked into DNC computers, then leaked the roughly 20,000 emails to WikiLeaks would be “irresponsible.”

"We never reveal our sources,” Assange also said, from Ecuador's embassy in London, where he is seeking refuge. "We don't give any material away as to who are our sources. It’s a security matter for us."

The July 22 release showed DNC staffers appeared to undermine the campaign of Democratic presidential candidate Sen. Bernie Sanders, which forced group Chairwoman Rep. Debbie Wasserman Schultz, a supporter of then-party front-runner Hillary Clinton, to resign. 

The release also created a rocky start for the Democrats' four-day convention last week in Philadelphia, where Clinton accepted the party's presidential nomination.

And the timing of the release sparked widespread speculation that Russian President Vladimir Putin, whom Republican nominee Donald Trump has at times seemed to admire, was behind the leak.

Such speculation was further fueled when Trump suggested that if Russia has emails that Clinton permanently deleted from her private server system while secretary of state, then the country should also leak them.

Trump later suggested that he was talking sarcastically. And he told ABC's "This Week" that he has no connection with Putin.

Assange on Sunday sought to focus on the content of the emails and their veracity, not who provided them.  

He said WikiLeaks has a "a perfect track record” with leaked material.

"What I can say categorically is that we have published proof that the election campaign of Bernie Sanders was sabotaged in a corrupt manner,” he also said.