Bernie Sanders will concentrate on winning California next, while Hillary Clinton will focus on the November general election.
Both Democratic US presidential candidates grabbed victories in Tuesday's primaries.
Hillary Clinton won in Kentucky, while Bernie Sanders won in Oregon.
Clinton's narrow victory in Kentucky by less than 0.5 percent of the vote was unexpected.
She spent two days campaigning there, with the aim of locking down the party nomination as the Nov 8 presidential election draws closer.
Clinton wants to be able to turn her attention to preparing for a face off with the presumptive Republican nominee, Donald Trump.
But she's still 100 delegates short of securing the nomination.
Sanders' win in Oregon boosted his momentum going into the June 7 vote in California - the biggest state in the US.
Oregon, together we are taking on virtually all of the Democratic establishment. Thank you for the strong victory! pic.twitter.com/nH7fI6QXU7— Bernie Sanders (@BernieSanders) May 18, 2016
Despite Clinton's sizeable lead in delegates, Sanders has managed to keep up in the race pretty well so far.
He says he will stay in the race "until the last ballot is cast."