The couple who crashed a White House state dinner last week is declining to testify at a hearing on the controversy to be held Thursday by the House Homeland Security Committee, as the chairman of the committee threatened to subpoena them.

The panel is investigating the security breach that apparently enabled Tareq and Michaele Salahi to pass through security checkpoints and pose for pictures with President Obama and Vice President Biden — despite not being on the White House's guest list.

The Secret Service has acknowledged that the Salahis got into the Nov. 24 dinner because its security procedures at a checkpoint were not followed.

The couple insisted in a TV interview that they were invited to the dinner. But e-mails between the Salahis and a friend who works at the Pentagon show they had tried to obtain an invitation but never were cleared to attend the exclusive party.

Secret Service Director Mark Sullivan will testify, but the White House has rejected an invitation extended to Social Secretary Desiree Rogers, who was in charge of the guest list, potentially setting up a battle over whether to issue a subpoena to her.

House Homeland Security Committee Chairman Bennie Thompson, D-Miss., told Fox News the committee will decide Thursday as to whether the panel will attempt to compel the attendance of the Salahis. He said he intends to pursue that option, because their testimony is "important to explain how a couple circumvented layers of security" at the state dinner.

The Salahis' attorney met with Homeland Security staff Thursday afternoon.

In a statement released late Wednesday night through their spokeswoman Mahogny Jones, "The Salahis said that they felt they had provided all relevant information to the committee and there is nothing further that they can do to assist Congress in its inquiry regarding White House protocol and certain security procedures. They therefore respectfully decline to testify."