In messages Friday on Twitter, the U.S. Embassy in Nigeria said it was "deeply disappointed" over the pardon issued this week of former Bayelsa state Gov. Diepreye Alamieyeseigha, who was impeached and later convicted in Nigeria. Investigators said he likely stole millions of dollars while in office.
Nigeria's President Goodluck Jonathan once served as Alamieyeseigha's deputy. His impeachment marked the start of Jonathan's rise in Nigerian politics.
The embassy said: "We see this as a setback in the fight against corruption." Embassy spokeswoman Deb MacLean said Friday that officials had no further immediate comment.
Nigeria is a top U.S. crude oil supplier.
In Washington, State Department spokeswoman Victoria Nuland said the "recent pardons of corrupt officials by the Nigerian government" are a setback for the U.S. support to strengthen the rule of law in Nigeria, "which is very important for the future of the country."
She hinted that the pardons could have repercussions on U.S. assistance programs.
"We have made clear to the Nigerians that this puts a question mark on the kinds of work that we've been trying to do with them," she said. No sanctions or punitive measures have been taken, she said, "but we're continuing to look at what's appropriate."
AP Writer Bradley Klapper contributed to this piece from Washington