A US plan to rehabilitate sanctioned tankers to boost oil supply may attract only a sliver of the dark fleet, as existing contracts, complex compliance checks and sky-high freight rates reduce incentives for would-be sellers.

The measure — detailed on Monday, just weeks ahead of the US midterm elections — is the latest in a string of efforts by the Trump administration to cool crude and fuel prices driven higher by months of war in the Persian Gulf and the ongoing conflict between Russia and Ukraine. Soaring gasoline and diesel costs in particular have fueled affordability concerns among US voters. But with limited numbers of sanctioned supertankers actually available and would-be sellers unwilling to forgo lucrative crossings in the Middle East, industry analysts say the effort to revive so-called dark vessels may struggle to gain traction.

“Sanctions relief does not equal immediately usable mainstream tanker capacity,” said Rahul Kapoor, global head of shipping analytics and research for S&P Global Energy. “The number of vessels that could realistically migrate back into mainstream trading would likely be materially smaller than the overall sanctioned fleet.”Under the US proposal, blacklisted vessels can be sold and rejoin the legitimate fleet, Energy Secretary Chris Wright said on Monday, adding the government would “convert” tankers to expand global availability but would not lift existing sanctions. He did not detail the sale process or potential investors.

The US has previously removed vessels from its sanctions list if they met certain conditions. The supertanker Kiara M was blacklisted in December for supporting the Venezuelan oil trade, but was then deleted from the list in March after Washington moved Caracas’s oil trade to the mainstream.

A wider plan would meet different hurdles — including the absence of financial incentives to sell up. Even though ships’ resale values have climbed in recent months, soaring freight rates mean that shipowners are still motivated to keep their vessels operating. A supertanker shuttling through the Strait of Hormuz can fetch as much as $40 million per trip, shipbrokers say. That compares to an early October price tag of about $190 million for a 10-year-old vessel, according to Clarksons data.

There are also practical challenges, including the simple availability of vessels not already under contract, and the fact that the European Union and the United Kingdom not only also blacklist vessels but also dominate maritime insurance cover, potentially limiting unilateral efforts.

Then there is age. Oil Brokerage, an independent energy broker, estimates that there are 294 sanctioned tankers free from EU or UK penalties — but 70% of them are above 20 years old and unpalatable to mainstream traders. That leaves just 75 commercially available tankers of all sizes, including 50 supertankers.

“Any capacity return is likely to be gradual rather than immediate,” Oil Brokerage analyst Ting Jun Jie said.

Fuel costs have been a pressing concern for the Trump administration, and efforts to cool oil prices over recent months have included periodic waivers on sanctioned oil and a diesel export deal with Russia. Brent remains near a five-month high, however, and a supercharged freight rally shows no signs of slowing.

“The administration is doing all these things to bring down prices,” said Karnan Thirupathy, partner at Wotton Kearney who advises clients on sanctions compliance and other regulatory issues on global shipping. “It hadn’t been framed that way in the past. It’s an indication that they’re more inclined to do this more now than before.”