Elise Amendola, Associated Press
Republican presidential candidate former House Speaker Newt Gingrich gestures as he participates in a one-on-one debate with former Utah Gov. Jon Huntsman in Manchester, N.H., Monday, Dec. 12, 2011.

ATLANTA — Newt Gingrich is urging supporters and staff to refrain from attacks on his Republican presidential rivals.

Gingrich's campaign released a letter Tuesday in which he pledges to run a positive campaign free of negative advertising. But the former House speaker also said he reserves the right to respond when his record has been distorted

As an example, he noted a "frank exchange" with rival Mitt Romney at last weekend's debate, when the two sparred over their private sector records.

Gingrich asks supporters in the letter not to contribute to any super PAC that runs negative ads against any other Republican contender.

He said it's critical that the GOP nominee emerge from the primary "unbloodied" and able to make the case against President Obama from a position of strength.