Gov. Chris Christie is urging political ally Mitt Romney to immediately release his tax returns rather than waiting until April.

The New Jersey governor tells NBC's "Today" that Romney should "put them out sooner than later because it's always better to have full disclosure."

Romney's taxes have emerged as an issue days before the South Carolina primary. He agreed in Monday night's debate to consider making his returns public, and then on Tuesday committed to releasing them in April. But the multimillionaire candidate now is on the defensive after acknowledging that his effective tax rate is 15 percent.

He says most of his income came from investments and speeches rather than earned income. Christie says he wants to remain as governor, but he wouldn't rule out joining a Romney ticket.

 (Copyright 2012 by The Associated Press. All Rights Reserved.)

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