The State Department said Tuesday it welcomes Boeing's announcement of a deal with Iran Air, and that it involves the "type of permissible business activity envisioned" in the Iran nuclear deal.

"The State Department welcomes Boeing's announcement of this deal with Iran Air," State Department press secretary John Kirby said at a briefing. "Boeing has been in close contact with the State Department regarding this deal."

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Meanwhile, Rep. Peter Roskam (R-Ill.), a member of the Ways and Means Committee, said he would work to block the transaction.

"If this moves forward, Boeing and terror will be intertwined," he told USA Today. "Congress will not be sitting by idly without something to say about it."

Boeing Co. announced earlier Tuesday that it had signed an agreement with Iran Air "expressing the airline's intent" to buy its aircraft, in what would be the biggest business deal between Iran and a U.S. company since 1979.

Kirby said the U.S. committed to license sales of civil passenger aircraft as a part of the Iran deal, which lifted sanctions on Iran in exchange for limits to its nuclear program.

"The [Joint Comprehensive Plan of Action] provides an opening for civil aviation companies, including American companies, to pursue legitimate commerce with Iran and we note reports of progress in the aviation sector, which is good both — for both the economy and for public safety," he said.

Iranian officials say they may purchase $25 billion in airplanes from Boeing. Iran's transportation minister, Abbas Akhoundi, told The Associated Press that the first Boeing plane could arrive in Iran in October if the deal goes through.

Boeing said in a statement to The Hill on Monday that "any agreements reached will be contingent on U.S. government approval."

House Republicans have warned the deal could have serious national security implications.

On Monday, Roskam and House Financial Services Committee Chairman Jeb Hensarling (R-Texas) sent a letter to Boeing CEO Dennis Muilenburg, arguing that U.S. businesses should not take part in “weaponizing” Iran’s regime.

The lawmakers argue that Iran's military frequently uses commercial airliners to transport troops, weapons and missiles around the world to groups like Hezbollah and Hamas and the Bashar Al-Assad regime in Syria.

Iran is also still listed by the State Department as a state sponsor of terrorism.

“These terrorist groups and rogue regimes have American blood on their hands,” they wrote. “Your potential customers do as well.”

The congressmen have asked Boeing to answer 10 questions about its negotiations with Iran by July 1.

Kirby said he was not aware of any other similar case where a U.S. manufacturer had been given a license to sell planes to a state sponsor of terrorism, but that the Iran deal laid out "appropriation conditions" for such sales, including banning its resale or transfer to anyone on a special designated list.

Vicki Needham contributed to this report.