DES MOINES (Reuters) - Social conservative Rick Santorum and former Massachusetts Governor Mitt Romney were tied at 24 percent of the vote in the Iowa Republican presidential caucuses on Tuesday after more than half the precincts reported, CNN and Fox News said.

The two pulled ever so slightly ahead of libertarian Ron Paul, who was third at 22 percent, while former U.S. House of Representatives Speaker Newt Gingrich was in fourth at 13 percent. The candidates are seeking the Republican nomination to face Democratic President Barack Obama in the November 6 U.S. presidential election.

(Writing by Mary Milliken)