The Scotland international scored 12 times for the West Midlands club last season, but they were still relegated from the Premier League last season.

The Black Cats host Reading in the top-flight on Saturday afternoon and O'Neill is hoping to have the 25-year-old in the squad to face the Royals.

"Fletcher has passed a medical and agreed personal terms," O'Neill told reporters. "We're just trying to do paperwork before the noon deadline."

Sunderland have been linked with Fletcher ever since he handed in a transfer request at the beginning of August, and the former Burnley forward joins Louis Saha on Tyneside in a new-look front line.

Wolves signed Fletcher from Turf Moor for seven million pounds in 2010 and will owe his former club 15 percent of the profit they will make on the striker.