BUENOS AIRES, Argentina (JTA) — Two U.S. congressmen expressed concern over Argentina’s decision not to allow its prosecutor in the Buenos Aires Jewish center bombing to testify at a House hearing on Iran’s influence in South America.

Reps. Michael McCaul (R-Texas), chairman of the House or Representatives’ Committee on Homeland Security, and Jeff Duncan (R-S.C.), chairman of its subcommittee on oversight and management efficiency, sent a letter Monday to Argentinian President Cristina Fernandez de Kirchner with their concerns about the decision to deny Alberto Nisman, general prosecutor of the AMIA center case, the opportunity to testify in Washington on Tuesday.

“Mr. Nisman was invited to share the findings from his October 2006 and May 2013 investigations into the AMIA bombings, which placed responsibility for the attacks on the highest authorities within the Government of Iran,” McCaul and Duncan said in the letter. “Furthermore, his investigation underscored a critical issue to U.S. Homeland Security, showing that Iran was ‘the main sponsor’ of an attempted attack in June 2007 on American soil to blow up John F. Kennedy (JFK) airport in Queens, New York. Had the plot not been uncovered, an untold number of Americans could have been killed by this terrorist act.

“The Government of Argentina has indicated its desire to pursue justice and truth on Iranian involvement in the AMIA bombing.  However, the decision to deny authorization for Mr. Nisman to testify before the U.S. Congress does call into question the authenticity of your intentions, and we are deeply disturbed.”

Last week, Argentinian Prosecutor General Alejandra Gils Carbo blocked Nisman from testifying at the Committee on Homeland Security  hearing on “Iran’s Extending Influence in the Western Hemisphere.”

Nisman maintains that Iran infiltrated several South American countries through the installation of intelligence centers.

The Iranian government in May officially agreed to establish a “truth commission” with Argentina to jointly investigate the 1994 attack on the AMIA center that killed 85 and injured hundreds.

Argentina’s Congress had ratified the collaboration in February over the protests of Jewish leaders.