WASHINGTON - Wisconsin Governor Scott Walker officially confirmed Monday he was joining the crowded field of Republicans jostling for the party's 2016 nomination as US presidential candidate. Walker, who went from relative obscurity to national attention because of his protracted battle with labor unions, declared his widely expected White House run on Twitter and was due to make a speech in his home state later in the day. "I'm in. I'm running for president because Americans deserve a leader who will fight and win for them," he wrote.

Walker, 47, becomes the 15th major Republican to join the race. A 16th, Ohio Governor John Kasich, is expected to enter later this month.