Mr O'Neill left New Zealand on Sunday with a contingent from the National Rural Fire Authority Response Team in order to help fight the extensive blazes.
The team was due to arrive at the National Interagency Fire Centre in Boise, Idaho, for a briefing on Monday before being deployed to Washington, Montana, California or Oregon.
Mr O'Neill was deployed as a strike team leader, and was expected to work in rugged, mountainous terrain.
His two-week assignment could be extended by a further two weeks, depending on the success of containing the fires.
National Rural Fire Officer Kevin O'Connor said the team of specialists from New Zealand had been joined by 60 firefighters from Australia.
High temperatures, dry conditions and lightning strikes have been hampering the efforts of thousands of United States firefighters and army volunteers.
New Zealand team members, drawn from rural fire authorities around the country, would provide front-line support to United States firefighters.
Mr O'Connor said the New Zealanders' logistics skills would be in high demand, especially managing aircraft to fight fires and ferry supplies to remote locations.
''They are likely to be working in rugged, mountainous terrain, which will make for a demanding deployment, especially in the very high temperatures gripping those states at the moment,'' he said.
New Zealand firefighters have helped their American counterparts seven times during the past 15 years.
