WASHINGTON — Democratic presidential rivals Barack Obama and Hillary Rodham Clinton took their fight over gas price relief to the morning talk shows today as they braced for the crucial Indiana and North Carolina primaries.

In comments on most major cable and network programs, the two White House hopefuls expressed confidence in their chances of winning the Tuesday contests but refused to predict that voting this week would be decisive enough to end the primary fight and begin the general election against putative GOP nominee John McCain.

On NBC's "Today" show, Obama predicted that after the final contests June 3 in Montana and South Dakota, "We will be in a position to make a decision who the Democratic nominee is going to be," he said. "I will be the Democratic nominee."

Clinton refused to predict Tuesday's results, but said her campaign has made up some ground after falling behind.

"I think we've closed the gap," she said on CNN's "American Morning."

Much of the exchange Monday centered on proposals Clinton has embraced to give drivers some relief from soaring gas prices. Clinton pushed her plan for a summer suspension of the gasoline tax, which she would pay for with a windfall profit tax on oil companies.

Obama called that plan a gimmick, and many economists expressed skepticism. In a CBS News/New York Times poll released Sunday, 49 percent of voters said they thought lifting the gas tax for the summer was a bad idea. Only 45 percent thought it was a good idea.

"I think a lot of people don't understand my plan," Clinton responded on CBS' "The Early Show."

"I want to the oil companies to pay that $8 billion this summer instead of having the money come out of the pockets of consumers and drivers."

For his part, Obama rolled out a new TV ad for Indiana and North Carolina that derided "Clinton gimmicks that help big oil."

Asked to respond, Clinton on Sunday had said: "I'm not going to put my lot in with economists because I know if we did it right ... it would be implemented effectively."

Does that mean she would not, as president, seek the advice of economists, Clinton was asked Monday on NBC?

"Oh no, of course not," she replied.

Obama is ahead in the hunt for convention delegates — 1,742.5 to 1,607.5, according to an Associated Press count Sunday — but he has faced a spate of troubles over the past month. That has Clinton sensing an opening. Still, the delegate math works in Obama's favor, and it will be difficult for Clinton to overtake him.