If he launches a presidential campaign, Jim Webb would not cooperate with a super PAC, the former Virginia senator promised Tuesday.

In an interview with the Des Moines Register editorial board, Webb (D) said that while legally he couldn’t stop someone from setting up a super PAC on his behalf, he was against the idea.

“If it violates your ethics, I think you should not participate,” he said. “I don’t want a super PAC. ... I wouldnt cooperate with one; it violates my sense of how the government system ought to work.”

Vermont Sen. Bernie Sanders (I), who has already launched a Democratic campaign, has also pledged not to accept super PAC support. Yet he has not been able to stop supporters from trying to raise unlimited funds in his name.

Former secretary of state Hillary Clinton, the overwhelming front-runner in the primary, has met with top donors to a super PAC supporting her bid. A super PAC is also helping former Maryland governor Martin O’Malley, who launched his campaign late last month.

While Sanders has promised he will have enough money to launch a serious campaign, Webb continues to express public uncertainty over his financial viability.

“We need to be able to know that we can raise enough money to get out and do the travel and build the staff,” he said, “be maneuverable, for lack of a better term.”

He has also continued to shy away from direct attacks on Clinton.

“That’s for you to decide,” he told the board members when asked what Clinton’s weaknesses were.

Like O’Malley, Webb — should he run — will have to define himself against both Clinton and Sanders, whose outspoken liberalism has attracted big audiences in Iowa. Webb is more conservative than the rest of the field on some issues and as or more liberal on others; on Tuesday, he reiterated his opposition to both cap-and-trade environmental legislation and fast-tracking a major Asian trade deal. He has heavily emphasized his experience with war and conflict, noting Tuesday that he has worked in the Defense Department, served in the Marines and reported from combat zones as a journalist.

But Webb also walked back an apparent criticism of Secretary of State John Kerry, whose style he had earlier called “jet-setting diplomacy.”

“I’m not going to criticize anybody for a job they’re trying to do,” Webb said, while reiterating that he thought there were border security issues that deserved Kerry’s attention.

Webb said Monday that he would decide whether or not to launch a bid within two weeks.