New Zealand have won the toss and elected to bat first in the World Cup final against England at Lord's, where both teams will be looking to win the tournament for the first time.
Both teams are unchanged from their semi-final victories earlier in the week, with England star Jonny Bairstow cleared to play despite suffering a minor leg injury against Australia on Thursday.
The start of the match has been delayed by 15 minutes due to some morning rain in London, but the weather is set to be fine for the rest of the day.
Speaking on Saturday, Williamson said he has no problem that England have been branded favourites for the tournament decider but says anything is possible.
The new 50-overs world champions will emerge at Lord's after what many consider will be a battle between England's deep batting line-up and New Zealand's incisive bowling attack.
England ruthlessly destroyed five-times champions Australia to move to the cusp of their first ever men's 50-overs World Cup title, while New Zealand's crafty bowlers defended a small total against two-times champions India in the other semi-final.
Squads
England: Jason Roy, Jonny Bairstow, Joe Root, Eoin Morgan (c), Ben Stokes, Jos Buttler (wk), Chris Woakes, Liam Plunkett, Adil Rashid, Jofra Archer, Mark Wood
New Zealand: Martin Guptill, Henry Nicholls, Kane Williamson (c), Ross Taylor, Tom Latham (wk), Jimmy Neesham, Colin de Grandhomme, Mitchell Santner, Matt Henry, Lockie Ferguson, Trent Boult