WASHINGTON (AFP) - Democrats in the US capital Washington went to the polls Tuesday (June 14) to cast ballots in the last remaining primary of the marathon 2016 presidential campaign, but the contest comes a bit late, with Hillary Clinton already the presumptive nominee.

Polls opened at 7am, with voters choosing between Clinton - who last week reached the magic number of delegates needed to lock up the nomination - and Senator Bernie Sanders of Vermont.

Clinton is expected to do well in the city, which has a large African-American population.

Republicans in Washington held their party convention in March, with Donald Trump emerging as the top vote-getter. Trump is now the presumptive GOP nominee.

Sanders, who so far has refused to concede the race to Clinton, said over the weekend that he plans to meet with her late Tuesday to discuss the Democratic party platform ahead of next month's convention in Philadelphia.

Sanders met at the White House last week with President Barack Obama, who endorsed Clinton a short time later.