Although the exact text of the resolution is still not known, the US has said it will file a motion that buttresses Pillay's recommendations made after a controversial visit to Sri Lanka in August when she declared that the Rajapakse administration was becoming increasingly authoritarian.
The government said this week that Pillay's recommendations reflected "bias and is tantamount to an unwarranted interference in the internal affairs of a sovereign state".
Rajapakse said he was committed to ensuring investigations into any allegations of wrongdoing by his security forces and challenged his accusers to provide evidence.
"I advocated investigations into disappearances in 1989 and 90 (during an uprising by Sinhalese Marxist rebels). Even today, I believe in it (human rights)," Rajapakse said.
Sri Lanka has previously said it needs more time to address issues of accountability and reconciliation after ending the Tamil conflict, which according to UN estimates claimed at least 100,000 liv