The White House late Wednesday promised to veto new legislation—first disclosed by the Washington Free Beacon—that would bar the administration from making “future ransom payments to Iran,” prompting outrage from key members of Congress who have been investigating how U.S. officials delivered nearly $2 billion in cash to Iranian officials.

The administration’s veto threat comes as top lawmakers on a range of investigatory committees launch efforts to uncover details about the cash exchange still being hidden by the Obama administration.

Congressional sources who spoke to the Free Beacon raised questions as to why the Obama administration would threaten to veto the bill, given its insistence that the cash payments to Iran were not part of a ransom.

“President Obama’s veto threat on our ransom legislation puts the lives of U.S. citizens around the world at risk,” Rep. Mike Pompeo (R., Kan.), a member of the House Intelligence Committee who helped spearhead the ransom legislation, told the Free Beacon.