Republican voters in the US state of Nevada are taking part in caucuses to decide the state's choice of presidential nominee.
Registered Republicans in each precinct are voting for candidates between 17:00 and 23:00 GMT on Saturday, although an evening caucus to allow observant Jews to participate will finish later.
After a strong result in Florida's primary on Tuesday Mitt Romney is hopeful of taking the western state.
Opinion polls put him in the lead.
Mr Romney won the state in his previous bid to be the Republican presidential candidate in 2008.
He has won two out of the four contests already held this year, Florida and New Hampshire, and came second in Iowa.
His main challenger, former congressman Newt Gingrich, has said he expects Mr Romney to come first in Nevada, partly due to the state's high Mormon population. Mr Romney is a Mormon.
There are two other candidates remaining in the race, Rick Santorum and Ron Paul.
Nevada has a population of 2.7m but only its 470,000 registered Republicans are eligible to vote in Saturday's caucuses.
The votes are the latest stage in the state-by-state process of picking a Republican nominee to challenge Democratic President Barack Obama in November's general election.
The Republican candidate will be formally selected by delegates at the party's convention in August.