U.S. defense officials on Thursday responded angrily to WikiLeaks' plan to post additional Afghan war logs, with Defense Secretary Robert Gates suggesting that the move could further endanger the lives of Afghans who helped the U.S. war effort.

WikiLeaks founder Julian Assange, speaking to a group in London by video link on Thursday, said his group had gone through 7,000 of the 15,000 documents the group has so far withheld from publishing. WikiLeaks had said it was withholding posting those documents until it had time to review them to block out the names of sources contained in the documents.

"Absolutely," he replied when asked whether he still plans to publish the remaining documents.

The organization has already released some 76,000 classified documents covering the war in Afghanistan from 2004 to 2010, leaked by a source the website has refused to identify.

The U.S. says it is investigating army intelligence analyst Bradley Manning as a possible source of the leak.

The documents touch on unreported incidents of Afghan civilian killings by North Atlantic Treaty Organization forces and covert operations against Taliban figures, among other things.

Pentagon Press Secretary Geoff Morrell said posting more documents would be "the height of irresponsibility."

"The only responsible course of action for them is to immediately remove all the stolen documents from their website and expunge all classified material from their computers," he said.

Earlier Thursday, Mr. Gates, responding to a question from a Navy sailor in San Diego, said intelligence sources have confirmed that al Qaeda and Taliban leaders have given direction to comb the documents looking for the names of Afghans who had helped the American war effort.

"I think the consequences are potentially very severe," Mr. Gates said. "We don't have specific information of an Afghan being killed yet because of them. But I put the emphasis on 'yet.' "

WikiLeaks' supporters say the accounts of the conflict should be publicized to reveal potential war crimes and the toll of the war.

Mr. Assange said some of the criticism has been "legitimate," but repeated his earlier call for the Pentagon and human-rights groups to help him redact the names. "So far there has been no assistance," he said.

He expressed some ambivalence about the need to protect Afghans who have helped the U.S. military. "We are not obligated to protect other people's sources," including sources of "spy organizations or militaries," unless it is from "unjust retribution," he said, adding that the Afghan public "should know about" people who have engaged in "genuinely traitorous" acts.

Mr. Assange said he still fears that the U.S. is trying to have him arrested for publishing the classified documents. He was meant to appear in person at the panel discussion about the media at London's Frontline Club, but dialed in by Skype instead. Asked by an audience member for his current location, he said "no comment." He appeared to have dyed his trademark white hair brown, and to have cut it in a close crop.

Write to Jeanne Whalen at jeanne.whalen@wsj.com