Democratic White House hopeful Barack Obama on Saturday defeated rival Hillary Clinton in caucuses on the tiny US Pacific island of Guam, a small but welcome victory after several rough weeks on the campaign trail.

Obama won the island's caucuses by seven votes, winning 14 of the island's 21 districts and finishing with 2,264 votes against 2,257 for Hillary Clinton, local party officials said.

It was not immediately clear whether the four pledged delegates from Guam's caucuses would be split evenly between Obama and Clinton -- Guam, like most Democratic Party nominating contests, uses a complicated formula of proportionally doling out the spoils based on a variety of factors.

Hillary Clinton issued a statement congratulating Obama for "running a vigorous campaign” and said she looks "forward to our next contests in Indiana and North Carolina."

Voter turnout on the island more than 12,900km from Washington was 25 percent higher than the4,000 party officials expected on Saturday. The island's residents, while US citizens, cannot vote in November's presidential election.