Pressure is building on Vermont Senator Bernie Sanders to give up his fight for the Democratic presidential nomination.
Hillary Clinton has been declared the presumptive Democratic nominee after winning four out of six primaries on Tuesday.
Sanders has virtually no path to the nomination but has vowed to fight on. He will meet US President Obama today.
Democrats have urged Sanders to join Clinton as she tries to defeat Donald Trump.
The billionaire businessman, seen as an outsider early in the campaign, is the Republicans' presumptive nominee.