A letter drafted by Reps. Jesse Jackson Jr. (D-Ill.) and Mike Pence (R-Ind.) urging swift, tough sanctions on Iran will be mailed to President Barack ObamaBarack ObamaClinton camp: Trump's fundraising 'bragging is total bunk' Football coach Ditka: 'Happy' to speak at GOP convention but not invited Obama blames ISIS for Istanbul attack MORE on Monday with 366 House signatures.
Late Friday afternoon, Jackson's office said they were still in the process of gathering the hundreds of signatures on the letter.
"We cannot allow those who would oppose or delay sanctions to govern either the timing or content of our efforts," it says, in reference to the lack of support at the Security Council by veto-wielders China and Russia.
The letter calls on Obama to "fulfill your June 2008 pledge that you would do 'everything in my power to prevent Iran from obtaining a nuclear weapon,'" to "rapidly" implement the sanctions legislation when it comes out of conference and use whatever presidential powers at his means to impose "punishing measures" on Tehran.
Jackson and Pence, along with Majority Leader Steny Hoyer (D-Md.) and Minority Whip Eric CantorEric CantorLobbying world The Trail 2016: 11 hours, 800 pages, 0 changed minds Juan Williams: The capitulation of Paul Ryan MORE (R-Va.), as well as Reps. Ileana Ros-Lehtinen (R-Fla.) and Dan Burton (R-Ind.), confirmed the culmination of their effort at a Wednesday afternoon press conference.
"This is a moment where traditional loyalties and interests give way to the interests of the United States of America," said Pence, who characterized the letter to Obama as "firm but respectful."
In the Senate, a similar letter circulated by Sens. Charles SchumerCharles SchumerFormer Gillibrand aide wins NY House primary Senate faces critical vote on Puerto Rico Juan Williams: GOP sounds the sirens over Trump MORE (D-N.Y.) and Lindsey GrahamLindsey GrahamOvernight Defense: US blames ISIS for Turkey attack | Afghan visas in spending bill | Army rolls up its sleeves Senate panel passes bill that would create 4K visas for Afghans Trump: Rivals who don't back me shouldn't be allowed to run for office MORE (R-S.C.) had gathered 76 signatures as of Wednesday, but that number had climbed to 80 as of Friday.
"Preventing Iran from obtaining nuclear weapons remains a diplomatic imperative," the letter states. "But time is not on the side of those who seek to prevent a nuclear Iran.
"... We urge you to move quickly to implement your existing authority on Iran and the legislation we send you, and to galvanize the international community to take immediate, substantive steps. Now is the time for action focused on preventing a nuclear Iran. We look forward to working with you on this important task."
In December, the House approved 412-12 a measure enabling Obama to ban foreign firms that supply Iran with refined petroleum from doing business in the U.S. The Senate passed its own version of sanctions targeting Iran's energy sector by voice vote on Jan. 28.
Next week, the House will move to instruct conferees and take the sanctions bill to conference.