HOUSTON - Sen. Hillary Clinton, D-N.Y., challenged rival Democratic candidate Barack Obama to four one-on-one debates ahead of the primaries in Texas and Ohio.

"Voters ought to have the opportunity to see these two candidates compete against each other in a one-on-one setting," Mark Penn, Clinton's chief strategist, told reporters.

Clinton agreed to a Feb. 28 debate in Houston at the request of The Greater Houston Partnership, The Houston Chronicle said Wednesday. NBC's Brian Williams and Tim Russert agreed to moderate the Houston debate.

Obama, D-Ill., has not yet committed to the debate.

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