A voter casts her ballot during the Republican Party presidential caucus in Bismarck, North Dakota, 5 Feb 2008

U.S. Republicans and Democrats in 16 states have picked the economy as the most important issue facing the country.

A survey of "Super Tuesday" voters conducted by Edison Media Research and Mitofsky International for the Associated Press and television networks shows Democrats ranked the war in Iraq second on their list of issues of concern, with health care third.

The survey shows Republican voters ranked immigration as the second-most important issue after the economy, followed by the war in Iraq.

In southern U.S. states in particular, issues such as the war in Iraq, taxes and religion were expected to weigh heavily with voters Tuesday. Voters in western states were expected to focus on national issues such as the economy, as well as specific issues, such as the environment and energy.