The United States has strongly condemned Sudan's granting of a presidential pardon to a man convicted in the jailbreak of four men sentenced to death for killing two US embassy staffers.
The pardoning of Mubarak Mustafa runs counter to previous assurances by Sudan that it would hold accountable all those involved in the murders, or who were responsible in any way, a statement from the American embassy said late Monday.
John Granville, an American working for the US Agency for International Development (USAID), and his driver, Abdelrahman Abbas Rahama, a USAID employee, died in a hail of bullets on New Year's Day 2008 in Khartoum.
Their killers, along with two co-conspirators, were convicted of murder in 2009 and sentenced to death. In June 2010, the four escaped by burrowing a tunnel, killing a Sudanese police officer and wounding another.
One of the men was later recaptured, while a second was believed to have been killed in Somalia in May 2011.
"Mubarak Mustafa was convicted of assisting the men to escape," the embassy said.
"In the interest of justice, we urge the government of Sudan to immediately rescind the pardon and return Mustafa to prison to serve out his term," it added.
"Failure to retract this pardon is contrary to the commitment of both the United States and Sudan to combat terrorism and hold accountable those responsible for terrorist acts."
In November Sudan's foreign ministry listed as top priorities the ending of US economic sanctions and removing Khartoum from the US State Department's sponsors of terrorism list.
Then-president Bill Clinton imposed the trade restrictions in 1997 over Sudan's support for international terrorism, efforts to destabilise neighbouring governments, and human rights violations.
The United States in January offered a $10 million reward for information leading to the capture of Granville's escaped killers, Abdelbasit Alhaj Alhasan Haj Hamad and Mohamed Makawi Ibrahim Mohamed.
They are believed to be hiding in Somalia.