Washington, July 16 (RHC)-- As nuclear talks between Iran and the P5+1 group continue in Vienna, two influential U.S. senators are calling for the imposition of more pressure on Tehran. The senators, Republican Lindsey Graham and Democratic Robert Menendez, urged other U.S. lawmakers to support demands that Iran accept at least two decades of tough international inspections of its nuclear program, before Congress would agree to ease sanctions.

In a letter to U.S. President Barack Obama circulated on Capitol Hill, Graham and Menendez said they want Iran to "come clean" about any military dimensions of its nuclear program. The senators said they feared an agreement between Tehran and the P5+1 group ending U.S. sanctions may "provide Iran a window for economic recovery where after it could resume its nuclear program."

The letter sought signatures by Wednesday, four days before the July 20th deadline for an agreement. Peace activists have denounced the letter as an attempt by hawks in U.S. Congress to derail the talks.

On Monday, U.S. Secretary of State John Kerry met with his Iranian counterpart Mohammad Javad Zarif in the Austrian capital. Zarif said at a press conference on Tuesday that talks might continue between the two sides beyond a July 20th deadline.

Kerry said that the latest round of talks has been positive and that he was returning to Washington "to discuss with President Obama and leaders in Congress over the coming days about the prospects for a comprehensive agreement as well as the path forward."