CRI听力:Kerry: Congress Can't Change an Iran Nuclear Deal

U.S. Secretary of State John Kerry is warning Congressional Republicans who control both houses they will not be able to modify any nuclear agreement struck between the United States and Iran.

Kerry's comments have come in response to an open letter written to Iran's leaders by a group of Republican senators, warning Tehran that a deal with President Barack Obama's administration could expire the day he leaves office.

The letter warns the Iranian side that a lasting agreement will need congressional support.

Testifying before the Senate Foreign Relations Committee, Kerry says the letter has undermined US foreign policy.

"It's incorrect when it says that Congress could actually modify the terms of an agreement at any time. That's flat wrong. They don't have the right to modify an agreement reached executive to executive, between countries.... between leaders of a country."

In response, Senator Rand Paul admits he signed the letter to send a message to the White House, which he says has repeatedly overstepped its authority.

US foreign policy has traditionally been the domain of the Executive branch of the US government.

However, Republicans, flush with power after winning the Senate in the last mid-term election, have been taking steps to undermine the White House's domain over international affairs, including sending the letter to Tehran, as well as inviting Israeli Prime Minister Benjamin Netanyahu to speak to Congress without consulting the White House.

Negotiations connected to Iran's nuclear program are due to resume in Lausanne, Switzerland, next week.

The talks are now at a critical juncture, as Iran and the world powers try to meet an end of March target for an interim agreement.

A final deal is scheduled to be finished by June.