Gordon Weiss, the UN spokesman for Sri Lanka, told Al Jazeera: "We hope that it will add to the assurances given to the UN secretary-general [Ban Ki-moon] by the president of Sri Lanka when he was here in May.
"The secretary-general believes that progress in getting people out of the camps and back home and on political reconciliation is going too slow.
"Sri Lanka has human rights obligations ... and is expected to uphold those obligations," he said.
The Sri Lankan government had promised Ban that 80 per cent of displaced people
would be sent back to their homes before the end of this year.
The foreign ministry said it welcomed Pascoe's visit and looked forward "to the widest possible engagements" during his stay.
Sri Lanka has so far resisted calls for war crimes investigations into its battle with the Tamil separatists.
The UN has said that up to 7,000 civilians may have been killed in the first few months of this year when security forces escalated their offensive against the remnants of the Liberation Tigers of Tamil Eelam (LTTE).
Sri Lanka has denied any civilians were killed by its security forces and in turn accused the Tamil Tigers of using tens of thousands of Tamil civilians as human shields, which Tamil leaders have denied.