Republican US Senate majority leader Mitch McConnell on Monday criticized the landmark deal on Iran's nuclear program, confirming that lawmakers opposed to the pact planned a formal response to the agreement.
"The administration needs to explain to the Congress and the American people why an interim agreement should result in reduced pressure on the world's leading state sponsor of terror,"  McConnell said in a statement following last week's marathon talks.
McConnell repeated his pledge to examine legislation proposed by Senators Bob Corker and Bob Menendez, which requires any deal on Iran's nuclear ambitions to be reviewed by Congress.
The Corker-Menendez bill would oblige President Barack Obama to give lawmakers 60 days to examine, and possibly block, a nuclear deal.
Obama has vowed to veto the bill in its current form, as well as a separate bill that would impose additional sanctions on Iran.
Republicans however are united behind the strategy of seeking to thwart an agreement, and have also won support from a sizable number of Democrats.
The powerful Senate Foreign Relations Committee is due to meet on April 14 to consider the bill, paving the way for its consideration by the full Senate before heading to the House of Representatives, also Republican-controlled.
Republicans have criticized the fact that the framework deal reached last week allows Iran to keep several thousand centrifuges, continue its research and development program and maintain a controversial underground laboratory at Fordo.
"Under no terms should the administration suspend sanctions, nor should the United Nations remove sanctions, until the Iranians reveal all aspects of the possible military dimensions of its previous research," McConnell added in his statement.
The Obama administration has mounted a political offensive aimed at giving him a free hand until June 30, the deadline for finalizing an Iran deal.
Obama last week warned Congress against moves to torpedo the Iran agreement.
"If Congress kills this deal, not based on expert analysis and without offering any reasonable alternative, then it's the United States that will be blamed for failure of diplomacy," Obama said Thursday.