The multiple Finnish champion will again run on DMACK tyres as the firm bids to prove it has improved its snow rubber.
DMACK struggled in Sweden last year, with the tyres off the pace and Ketomaa opting not to rejoin after an accident.
Dick Cormack, DMACK's motorsport director, is confident his product is much more competitive this year.
"We have a much improved winter snow tyre this year and expect it to be popular in both Latvia and Sweden," he said.
"Jari will be strong on these events and we're confident he can demonstrate how much progress we've made."
Ketomaa was runner-up in the inaugural Super 2000 WRC in 2010, led on his World Rally Car debut in Finland the following season, and then contested a partial campaign with Autotek's DMACK-shod Ford last year.
The ERC's Rally Liepaja-Ventspils takes place in Latvia on 1-3 February, with the WRC's Rally Sweden one week later.