The U.S. Postal Service on Wednesday said it is seeking to impose a temporary 8% fuel surcharge for package and express mail deliveries to deal with rising transportation costs, which include higher oil prices as a result of the Iran war.

If approved by the Postal Regulatory Commission, the surcharge would take effect April 26 and remain in place until Jan. 17, 2027, the Postal Service said in a notice on its website.

The 8% surcharge would apply to postage on Priority Mail Express, Priority Mail, USPS Ground Advantage, and Parcel Select products. First-class stamps and other mail services would not be affected.

Oil prices have jumped more than 40% since Feb. 28, when the United States and Israel attacked Iran.

“This temporary price adjustment will provide needed flexibility for the Postal Service by helping to ensure that the actual costs of doing business are covered, as required by Congress,” the Postal Service said in its announcement.

“Transportation costs have been increasing, and our competitors have reacted with a number of surcharges,” the notice said.

“We have steadfastly avoided surcharges and this charge is less than one-third of what our competitors charge for fuel alone, so even with this change, the Postal Service continues to offer great value in shipping with some of the lowest rates in the industrialized world.”

CNBC has reached out to the Postal Regulatory Commission for comment on the Postal Service’s request.

Federal Express on Monday sued the U.S. government, seeking a “full refund” of the money the shipping giant paid for tariffs unilaterally imposed last year by President Donald Trump, which the Supreme Court ruled last week were illegal.

FedEx’s suit appears to be the first filed by a major American company seeking a refund for tariffs after Friday’s Supreme Court decision.

Other companies filed lawsuits staking claims to their refunds before the high court ruled that the tariffs Trump imposed under the International Emergency Economic Powers Act are illegal.

Those suits, whose plaintiffs include retail warehouse club giant Costco, remain pending at the U.S. Court of International Trade in New York, the same court where FedEx filed its lawsuit.

The Supreme Court, in its ruling on Friday, said the Court of International Trade has “exclusive jurisdiction” over the IEEPA tariffs.

“Plaintiffs seek for themselves a full refund from Defendants of all IEEPA duties Plaintiffs have paid to the United States,” Federal Express Corp, and its associated company, FedEx Logistics, say in the new lawsuit.

The 11-page complaint names as defendants U.S. Customs and Border Protection, which collects tariffs, its commissioner, Rodney Scott, and the U.S. government.

CNBC has requested comment on the suit from CBP and the White House.

The suit does not say how much FedEx has paid in IEEPA tariffs since Trump imposed them on most U.S. trading partners last year.

But in September, FedEx had said that it expected it would take a $1 billion hit to its earnings for the fiscal year because of U.S. trade policies, not all of which involved IEEPA duties. That dollar amount represents 16% of total earnings for the prior fiscal year.

In a note on its website, FedEx said, “While the Supreme Court did not address the issue of refunds, FedEx has taken necessary action to protect the company’s rights as an importer of record to seek duty refunds from U.S. Customs and Border Protection.”

“At this time, however, no refund process has been established by regulators or the courts,” the company said. “We will communicate any relevant information and updates in a timely manner, and we appreciate your patience as we wait for additional guidance and clarity from the U.S. government and the courts.”