WASHINGTON — Mitt Romney began airing commercials Wednesday on national cable networks at a cost of some $2 million in an attempt to boost his standing among the leading Republicans seeking the presidency.

The campaign also renewed an ad campaign in Iowa and New Hampshire, a Romney adviser said. Most of the national ads will run on Fox News, a strategic effort by the campaign to reach conservative voters.

The adviser spoke on the condition of anonymity because the campaign does not publicize its ad strategy. In the national ad, called, "I like Vetoes," Romney, the former governor of Massachusetts, says that as president he would demand that discretionary domestic spending be capped at 1 percent less than the rate of inflation.

"If Congress sends me a budget that exceeds that cap I will veto that budget," Romney says. "I like vetoing."

Besides Fox, the ad also will run on CNBC, MSNBC and CNN. The total cost of airing the ads is expected to be about $2 million and will run for more than a month.

Romney spent about $2 million in the first three months of the year on advertising, a recognition that he was the least well-known of the leading GOP candidates for the presidency.

While the ads boosted some of his name recognition, he remains behind pack leaders Rudy Giuliani and John McCain and also has registered lower than actor and former Sen. Fred Thompson of Tennessee, who has not announced his intentions to run.

Romney raised $21 million in the first quarter and began the second quarter with nearly $12 million in the bank, the most money of the Republican candidates.