Holder's "Oh Shit" Gunwalker Moment: Melson "reportedly eager to testify to Congress about the extent of his and other officials' involvement."

Richard A. Serrano, Washington Bureau, of the LA Times writes: Federal ATF chief said to resist pressure to step down.

The acting director of the federal Bureau of Alcohol, Tobacco, Firearms and Explosives is strongly resisting pressure to step down because of growing controversy over the agency's surveillance program that allowed U.S. guns to flow unchecked into Mexico, according to several federal sources in Washington.

Kenneth E. Melson, who has run the bureau for two years, is reportedly eager to testify to Congress about the extent of his and other officials' involvement in the operation, code-named Fast and Furious.

Melson does not want to be "the fall guy" for the program, under which ATF agents allowed straw purchasers to acquire more than 1,700 AK-47s and other high-powered rifles from Arizona gun dealers, the sources said. The idea was to track the guns to drug cartel leaders. But that goal proved elusive, and the guns turned up at shootings in Mexico, as well as at the slaying in Arizona of a U.S. Border Patrol agent in December.

"He is saying he won't go," said one source close to the situation, who asked for anonymity because high-level discussions with Melson remained fluid. "He has told them, 'I'm not going to be the fall guy on this.' "

Added a second source, who also requested anonymity: "He's resisting. He does not want to go."

Melson has an open invitation to appear on Capitol Hill. So far, he has not been given Justice Department approval to appear before Congress.

This week, Rep. Darrell Issa (R-Vista), chairman of the House Committee on Oversight and Government Reform, said he hoped that Melson would give a full accounting of how the gun operation was conceived and carried out. He also said Melson should resign, and that other senior leaders at ATF and the Justice Department should be held accountable as well.

Sen. Charles E. Grassley (R-Iowa), ranking member of the Senate Judiciary Committee, also is awaiting answers from Melson, and cautioned this week that even if the acting director stepped down, it "would be, by no means, the end of our inquiry."

The Justice Department said it was cooperating with congressional leaders.

"We've been working with the [Issa] committee on interviews, including Melson, and will continue to do that," said Tracy Schmaler, a Justice Department spokesperson.

At ATF headquarters in Washington, officials said Melson "continues to be focused" on leading the agency. His chief spokesman, Scott Thomasson, added, "We are not going to comment on any speculations" about Melson's status as head of the agency.

At a House hearing last week, testimony from ATF agents portrayed Melson as closely involved in overseeing the venture. At one point, according to documents released by Congress, he asked for and received log-in information and a link to an Internet feed in order to watch some of the illegal straw purchases.