President Obama’s nominee to head the Bureau of Alcohol, Tobacco, Firearms and Explosives is scheduled to meet with senior Justice Department officials Tuesday amid growing pressure on the agency’s leadership over a controversial gun-trafficking operation.

Andrew Traver, who runs the ATF’s Chicago office, is arriving in Washington as political fallout is continuing from the agency’s “Fast and Furious” operation, which targeted Mexican gun traffickers but has been linked to the killing of a U.S. law enforcement officer. Republicans in Congress have criticized the ATF’s handling of the investigation.

One U.S. official, who spoke on the condition of anonymity to discuss internal deliberations, said Traver may be offered the ATF’s top job on an acting basis at a meeting Tuesday with Attorney General Eric H. Holder Jr. CNN reported Monday that the current acting director, Kenneth E. Melson, is expected to resign under pressure.

But law enforcement and other sources said Melson has told associates that he believes he has done nothing wrong. Officials said the White House is watching the situation warily and is concerned about the ATF but has not asked for Melson’s resignation.

The conflicting reports reflected the troubled state of a small agency that enforces federal gun laws but is itself increasingly in the crossfire. The ATF became part of the Justice Department after Sept. 11, 2001, and had a long-standing battle with the FBI over who controls investigations of bombings, which has drawn criticism from top Justice officials.

The ATF has been without a permanent director since 2006, when Congress required the position to be confirmed by the Senate. With the powerful gun lobby able to block a director because one senator can hold up a nomination, Obama in November nominated Traver, who is special agent in charge of ATF’s Chicago field division.

But the National Rifle Association strongly opposes Traver because the organization believes he is linked to gun-control advocates and anti-gun activities, the organization has said. His nomination has stalled in the Senate.

Melson, a former federal prosecutor in Alexandria and longtime Justice Department official, became the ATF’s acting director in April 2009. He is respected by many in law enforcement circles as an apolitical law enforcement professional.

But Melson’s stewardship of ATF has come under fire over the Phoenix-based operation dubbed “Fast and Furious.” Under pressure to snag bigger players in trafficking organizations smuggling weapons to Mexico, ATF launched the campaign in early 2010.

For nearly a year, agents tracked guns they suspected might end up in the hands of Mexican cartels.

Assistant Attorney General Ronald Weich said at a congressional hearing last week that the idea was to dismantle “a significant transnational gun-trafficking enterprise” and pointed out that the investigation has led to 20 indictments.

But it turned out that two of the AK-47s recovered at the scene of the fatal shooting of U.S. Border Patrol agent Brian A. Terry in December were bought in “Fast and Furious.” Several ATF agents testified at the hearing before the House Oversight and Government Reform Committee that the operation failed and that they were ordered not to stop people they suspected had the illegal guns.

Committee Chairman Darrell Issa (R-Calif.) introduced evidence that he said showed that Melson and other senior ATF officials were regularly briefed on “Fast and Furious.” Also last week, a report issued by Issa and Sen. Charles E. Grassley (R-Iowa) accused the Justice Department and ATF of allowing nearly 2,500 guns to flow illegally into Mexico as part of the program.

The Justice Department’s inspector general is investigating the allegations.

If Traver is offered and accepts the ATF director position on an acting basis, it is considered unlikely that he could win Senate confirmation. Since the position became Senate-confirmable, the gun lobby has effectively prevented any nominee from being confirmed.

Staff writers Anne E. Kornblut and James V. Grimaldi contributed to this report.