ALBANY — Orange County Executive Edward Diana is expected to announce as soon as today that he’ll challenge three other GOP contenders for the right to run against Democratic Sen. Kirsten Gillibrand.

Republican officials said yesterday that Diana, who has headed the county since 2002, has notified state GOP Chairman Edward Cox that he will likely enter the race.

Ex-Rep. Joe DioGuardi of Westchester, former PA board member Bruce Blakeman and economist David Malpass are already in.