Two key documents are missing from the Iran nuclear deal submitted to Congress, and the two leaders of the Senate Foreign Relations Committee want the Obama administration to hand them over, Chairman Bob Corker said Tuesday.

The Tennessee Republican said he and ranking Democrat Ben Cardin of Maryland wrote to request the missing documents, which he said deal with an Iranian military facility at Parchin and a side agreement Iran reached with the International Atomic Energy Agency.

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"We sent a letter today, both of us, asking the administration for the documents," he said.

Corker said he and Cardin also met with Energy Secretary Ernest Moniz earlier Tuesday to discuss the documents but did not give further specifics about them.

A Corker spokesperson later told the Washington Examiner:

"Senators Corker and Cardin sent a private letter to Secretary [of State John] Kerry requesting two additional documents associated with the Iran nuclear agreement that were left out of the materials required to be submitted to Congress per the Iran Nuclear Agreement Review Act that the president signed into law."

The 159-page deal reached in Vienna on July 14 and approved Monday by the U.N. Security Council requires Iran to resolve with the IAEA by Oct. 15 all outstanding issues related to its past nuclear work as a condition of the sanctions relief laid out in the agreement. The roadmap for that process is laid out in a side agreement signed on the same day by IAEA Director General Yukiya Amano and Ali Akbar Salehi, head of the Atomic Energy Organization of Iran.

The Iranian military facility at Parchin is widely believed to have been one of the locations where past nuclear weapons research was conducted.

Nonpartisan nuclear experts have noted that Iran's full accounting of any past nuclear weapons work is essential to establishing a baseline for international inspectors to verify the agreement, in which Iran swears off any intent to build a nuclear bomb and agrees to put most of its nuclear program on ice for 10 years in exchange for relief from sanctions that have crippled its economy.

The Institute for Science and International Security, one of the groups that has closely monitored the negotiations with Iran, warned in an analysis released Tuesday that the deal may contain a loophole in which Iran gets sanctions relief without that issue being resolved, and recommended that the United States and its allies clarify that point.

"The [agreement] does not state explicitly the consequences for Iran not addressing all of the IAEA's ... concerns," the analysis said.

Administration officials sent the nuclear agreement to Congress on Sunday, triggering a 60-day period for lawmakers to review the deal, during which President Obama cannot waive any sanctions enacted by Congress. Lawmakers must now vote whether to approve or disapprove of the agreement.

Kerry, Energy Secretary Ernest Moniz and Treasury Secretary Jack Lew will give senators a classified briefing about the agreement on Wednesday ahead of a public hearing Thursday before Corker's panel.

The three Cabinet members also are scheduled to appear before the House Foreign Affairs Committee on July 28.

Corker brushed off a question about whether the missing documents would change that timeline. "Actually we're more concerned at the present just with getting the documents," he said.