US President Donald Trump extended a review period overnight to October 12, 2017 before it makes a decision on whether or not to permanently lift the decades-old sanctions.
His predecessor Barack Obama had eased the sanctions in January, but kept Sudan on review for six months, a period that ended today.
Obama had made the permanent lifting of the sanctions dependent on the North African country's progress in five areas of concern at the end of the review period.
Khartoum expressed disappointment.
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"We regret such a decision that came out after long negotiations between Sudan and the United States," said Sudanese Foreign Minister Ibrahim Ghandour.
"The United States, Europe, Africa and the international community admit that Sudan has fulfilled its commitments when it comes to the five tracks, which is why we don't see any reason for extending the review period," he told reporters.
"But we are still hoping that the sanctions will be lifted permanently."
The areas of concern -- or "five tracks" -- include giving more access to humanitarian workers in war zones, counterterrorism cooperation with the United States, an end to hostilities against armed groups in Sudan and halting support for insurgents in neighbouring South Sudan.
Washington imposed a complex set of economic sanctions on Sudan in 1997 for its alleged backing of Islamist militant groups.
Al-Qaeda leader Osama bin Laden, who was killed in a US commando raid in Pakistan in 2011, was based in Khartoum from 1992 to 1996.
Washington also justified the embargo with accusations of scorched-earth tactics by Khartoum against ethnic minority rebels in war-torn Darfur.
President Omar al-Bashir is wanted by the International Criminal Court for genocide and war crimes related to the conflict, charges he steadfastly denies.
The UN said it had hoped the United States would make a "positive decision" on the sanctions against Sudan for allowing more humanitarian aid access across war zones as sought.
But some think-tanks had called for the review period to be extended, saying Khartoum needed to do more for the embargo to be lifted.
The Enough Project, a Washington-based think-tank, said the Trump administration should now devise a new set of "smart and modernised" sanctions that would spare the Sudanese people.