Officials with Royal Dutch Shell met recently in Tehran to discuss the work potential should sanctions pressure ease, the company confirmed.

Negotiators are working toward a June 30 deadline to formalize a framework agreement that gives Iran relief from sanctions in exchange for commitments to pull back from the brink of advancing with the technology needed to manufacture a nuclear weapon.

Iranian officials have said they're vetting interest from energy companies eager to return to the country and Shell spokesmen confirmed to UPI the Dutch supermajor is among that group.

"Shell officials recently met Iranian officials in Tehran," they said. "They discussed Shell's outstanding debt to National Iranian Oil Co. for crude lifted but not paid for, and potential areas of business cooperation should sanctions be lifted."

Shell maintained oil ties to Iran through pre-existing contracts before the European Union placed an embargo on Iranian crude oil mid-2012. A statement from 2013 read that Shell has about $2.3 billion payable to, and around $11 million receivable from, NIOC, though a settlement was impossible because of applicable sanctions.

Exxon Mobil in May said it was monitoring ongoing nuclear negotiations, but added it was "not lobbying on Iran sanctions."

Iran under the terms of a 2013 arrangement is exporting around 1 million barrels per day, about half of its full potential. The U.S. Treasury Department estimated Iran was out about $40 billion in revenue last year as a result of sanctions. In a briefing this week, the Energy Information Administration said formalizing the framework agreement could put more Iranian crude oil on the market.

"However, the ultimate decision and the timing that sanctions could be lifted are highly uncertain," it said.

Iranian Supreme Leader Ali Khamenei said in a late Tuesday speech there would be no commitments on a nuclear drawdown unless sanctions are "lifted immediately." U.S. State Department spokesman John Kirby said getting the right deal is better than when the deal materializes, but stressed the June 30 deadline is "what everybody's focused on."