WASHINGTON (Reuters) - As Hillary Clinton and Barack Obama battle to be the Democratic presidential nominee, the winner could be determined by primaries held weeks ago in Florida and Michigan, even though the party decided to ignore their results.

Both contests have been ruled unofficial because the states violated Democratic Party rules by moving their elections forward in a bid to have more influence in selecting the nominee.

Now Michigan and Florida’s 366 suspended delegates could prove decisive if neither candidate lands a knockout blow in the states remaining before the party’s August convention.

Party officials are trying to avoid an ugly standoff that could linger through the summer and anger the 2.4 million voters who participated in the two primaries, both swing states that may be crucial in the November election.

“The party is certainly concerned that some voters feel their votes didn’t count,” said Florida Democratic Party spokesman Mark Bubriski.

So far neither state has agreed to stage another contest.

Florida party officials say the state’s large elderly and military populations would have trouble participating in a caucus, while a mail-based election would cost up to $10 million.

Michigan Democratic Sen. Carl Levin said last week it would not be “practical or fair” to hold a caucus after 600,000 people have already voted in that state’s primary. Others have said it should not decide delegates because many stayed away from the polls on the belief their vote would not count anyway.

The Democratic National Committee had to suspend each state’s delegates to prevent 20 other states from moving up their contests to January, a spokeswoman said.

Slideshow ( 10 images )

“The rules were upheld to ensure a fair and predictable process and to stop other states from leapfrogging forward,” said Democratic National Committee spokeswoman Stacie Paxton.

Clinton, a New York senator and former first lady, won both contests, though Obama’s name was not on the ballot in Michigan.

Slideshow ( 10 images )

The candidates did not campaign in either state, but some Obama TV ads aired in Florida as part of a national package of advertisements, and Clinton flew in to celebrate her victory. Both attended fundraisers in the state.

Both state parties have since allocated their delegates to the national convention that picks the candidate. Clinton would get 178 from the two contests, while Obama would get 67 delegates from Florida. Some 55 delegates in Michigan are “uncommitted” since Obama’s name was not on the ballot.

As of Wednesday, Obama, an Illinois senator, had 1,078 delegates nationally to Clinton’s 969, according to MSNBC, not counting the party insiders and elected officials who as “superdelegates” can support either candidate.

The two candidates could agree on a solution with regard to Florida and Michigan, but that has not happened yet. If no agreement is reached, the convention’s credentials committee would have to decide in July who, if anyone, should be seated.

Clinton has said she will fight to seat both states’ delegates at the party convention, while the Obama campaign has said it would support another round of contests in those states if given adequate time to compete.

The Michigan and Florida primaries violated Republican Party rules as well, and the Republican Party responded by cutting each state’s delegate total in half -- a solution that drew relatively little protest from the states or candidates.

(Editing by David Wiessler)