US election 2012: Iowa caucus set for early January
Iowa Republicans have confirmed they will hold their presidential nominating caucus on 3 January 2012.
The vote was originally scheduled for February, but then Nevada set its date for 14 January.
Florida Republicans were the first to upset the calendar, when they moved forward their primary to 31 January.
Caucuses are town-hall style contests where voters decide which candidates win a group vote. Primaries are more traditional ballot votes.
Iowa's caucus and New Hampshire's state primary election are usually the first set of nominating contests, but Nevada and Florida's actions have left New Hampshire with fewer available dates in early 2012.
Florida's decision to schedule its ballot before March was in breach of national Republican party rules.
But it is Nevada's mid-January date that has "exacerbated" the scheduling problem for the so-called "first in the nation" contests, said Iowa Republican party chairman Matt Strawn.
Nevada has "unnecessarily crowded the January calendar", Mr Strawn said, adding: "Time remains for Nevada to respect the process, honour tradition and rectify the problem in a way that will restore order to the nomination calendar."
Democratic Senate Majority Leader Harry Reid has backed the move by Nevada Republicans.
A Reid aide told the Associated Press news agency that Nevada Democrats would hold their caucus on 14 January too, in solidarity with Nevada Republicans.
New Hampshire is now threatening to hold its primary in December, unless Nevada delays its vote.
New Hampshire could still leapfrog Iowa's date, but that would now mean scheduling in December around the holiday season.
New Hampshire Secretary of State Bill Gardner has the sole authority in his state to set the primary.
Mr Gardner's office told the Des Moines Register that while 10 January has been suggested, the state would not set its primary on that date as long was Nevada was scheduled for later the same week.
Correspondents say holding nominating contests so close together prevents candidates from capitalising on their success from one primary to the other, and often favours existing frontrunners.
Republican candidate Jon Huntsman has gone as far as focusing his entire campaign on New Hampshire.
Mr Huntsman, whose campaign is in financial trouble, says he will boycott the Nevada primary because of the date the state has set.
Five Republican candidates have followed suit, leaving former Massachusetts Governor Mitt Romney, Texas Governor Rick Perry and Senator Ron Paul campaigning in the state. But Mr Romney and Mr Perry have the most cash on hand.
Mr Huntsman will also boycott a Republican debate hosted in Nevada on Tuesday.