The U.S. Treasury Department on Monday slapped counterterrorism sanctions on key players in Iran's oil sector for supporting the Quds Force, the elite paramilitary arm of the Islamic Revolutionary Guard Corps. The move, just before the Nov. 3 U.S. election, followed sanctions on 18 banks in Iran that Washington imposed earlier this month.

Biden supports returning to diplomacy with Iran if it comes into compliance with the 2015 nuclear deal Washington struck with Tehran and five other world powers. Doing that could eventually add some 2 million barrels per day of Iranian oil to world markets that had been cinched off by President Donald Trump's wider unilateral sanctions on the OPEC member.

Analysts have said Monday's action was among moves by the Trump administration attempting to make it harder for a potential Biden White House to lift sanctions.

"It seems clear that one of the primary reasons for yesterday's action was to try to make it more difficult for a potential next administration to go back into the JCPOA," said Peter Harrell, a former State Department official and supporter of Biden, referring to the nuclear deal.

While Biden could remove Trump's new sanctions by executive order, he would pay a price.

"The new sanctions do not create a legal barrier to relieving sanctions under Biden," said Henry Rome, a senior analyst at the Eurasia Group, a consultancy.

Still, the new sanctions could "provide ammunition to congressional critics," who might say a Biden administration was glossing over Iran's support for terrorism if it sought a new deal with Tehran, Rome said.

It could also create added paperwork and bureaucratic process to unwind the raft of sanctions, making the effort marginally more difficult, experts said.

But Monday's sanctions could also offer Biden collateral when cutting an eventual deal, said Kevin Book, an analyst at ClearView Energy Partners.

"Biden can blame Trump for the strictures he put in place even as he offers their elimination as a source of goodwill during negotiations," with Iran, Book said.

Tristan Abbey, a former aide to Republican Senator Lisa Murkowski who worked at the national security council in the Trump White House, agreed. "A cynic would say it's more stuff they can barter away in a deal," said Abbey, now president of Comarus Analytics.

The White House did not comment. Neither did the Biden campaign.

Trump left the JCPOA deal in 2018, saying it did not do enough to curb the Iran's nuclear and ballistic missile programs and militant influence across the Middle East.

LITTLE LEFT TO DO ON SANCTIONS

The prospect of Biden getting to a new deal with Tehran if elected was already going to be a lengthy endeavor involving many months at least of multilateral talks.

The negotiations would likely come only after Iran takes steps on its nuclear program including downblending stocks of enriched uranium that have built up during the Trump administration, an action that would have to be verified by U.N.inspectors.

The U.S. Treasury on Monday blacklisted Iran's Ministry of Petroleum, the National Iranian Oil Company and the National Iranian Tanker Company alongside other individuals and entities. The move freezes any U.S. assets of those blacklisted and generally bars Americans from dealing with them.

At least two of the entities, NIOC and NITC, had already been sanctioned under different legal authorities, as the Trump administration carried out its "maximum pressure" policy on Iran.

Alireza Miryousefi, the spokesman for Iran's mission to the United Nations, pointed to the duplication as over reliance on sanctions by the Trump administration.

"The U.S. is sanctioning Iranian entities that have already been sanctioned under other phony charges," he said in a statement. "However, the U.S.' addiction to sanctions has not paid off as (the) U.S. national security adviser admitted ... the U.S. has out-sanctioned itself."

Miryousefi was referring to comments by Trump's national security adviser Robert O'Brien, who spoke over the weekend to reporters about the difficulties of using sanctions to stop meddling in U.S. elections.

"One of the problems that we have with both Iran and Russia is that we have so many sanctions out on those countries right now that there's very little left for us to do," O'Brien said. Washington was "looking at every potential deterrent" to stop the meddling," he said.

While the Trump administration is seeking to tie the hands of its successor on Iran, according to Harrell, now a sanctions expert at the Center for a New American Security, it is not clear if it will succeed.

"Legally, there's no reason another administration couldn't undo these sanctions, so it's fundamentally a call about has this changed the political calculus in some way," he said.

(Reporting by Timothy Gardner and Daphne Psaledakis in Washington; additional reporting by Michelle Nichols at the United Nations; Editing by Richard Valdmanis and Tom Brown)

By Timothy Gardner and Daphne Psaledakis