Washington ? Aides to State Department Inspector General Howard Krongard threatened two investigators with retaliation this week if they cooperate with a congressional probe into Krongard’s office, the chairman of a House of Representatives panel and other U.S. officials said Friday.

The allegations are the latest in a growing uproar surrounding Krongard. Current and former officials in his office charge that he impeded investigations into alleged arms smuggling by employees of the private security firm Blackwater and into faulty construction of the new U.S. Embassy in Baghdad.

Krongard has denied the charges and is due to appear before the House Oversight and Government Reform Committee next month.

In a statement e-mailed to reporters Friday, his office said it was cooperating with investigators.

“The Office of the Inspector General has cooperated with and will continue to cooperate with the House Oversight and Government Reform Committee’s investigation,” the statement said. “Furthermore, the OIG will continue to make any OIG employee available to speak with the committee, if they choose.”

Officials at the State Department and other agencies said support for Krongard appeared to be slipping and that it remained uncertain whether he could keep his job. They spoke on condition of anonymity, because Secretary of State Condoleezza Rice hasn’t made a final decision in the matter.

The probe into Krongard’s office is being led by Rep. Henry Waxman, D-Calif., the chairman of the House oversight committee.

The two investigators said they were threatened with retaliation – perhaps including losing their jobs – if they cooperated, Waxman said in a letter to Krongard.

Blackwater, which has received roughly $835 million in State Department contracts, mostly to guard U.S. civilians in Iraq, is under intense scrutiny after a series of violent incidents involving its contractors. In the most recent, Blackwater teams were involved in a shooting at a busy Baghdad traffic circle Sept.16 that killed 11 Iraqis.