Mr. Bush also used a joint news conference with Mexican President Felipe Calderon and Canadian Prime Minister Stephen Harper to renew his call for Congress to pass a free-trade pact with Colombia. He said House Speaker Nancy Pelosi's refusal to schedule a vote could effectively kill it this year.
"It makes no sense to me to say that Colombian goods can come into our country duty-free, yet our goods can't go into Colombia duty-free," Mr. Bush said sternly. "And yet that's the case. An agreement with Colombia would level the playing field."
Asked about the state of the U.S. economy, Mr. Bush said: "We're not in a recession. We are in a slowdown."
"I'm obviously concerned for our consumers," the president said. He was asked whether the rising cost for gasoline will erode the potential positive impact of the $168 billion economic stimulus package passed by Congress, but did not specifically answer.
"No question that rising gasoline prices are like a tax on our working people," Mr. Bush said.
Some of Mr. Bush's strongest words came in defending NAFTA, which took effect in 1994.
The three-way trade pact has been criticized by both Democratic Sens. Hillary Rodham Clinton and Barack Obama, who have promised to try to renegotiate the agreement if elected president. Mr. Bush's comments came on the day of the critical Pennsylvania primary, in which trade and the loss of manufacturing jobs in the United States has been a top issue.
"Now is not the time to renegotiate NAFTA or walk away from NAFTA," Mr. Bush said. "Now is the time to make it work better for all our people, and now is the time to reduce trade barriers worldwide."
Mr. Bush was asked if he thought he was losing the free-trade debate in the court of public opinion because of the strong opposition to NAFTA from the two Democratic rivals.
"My biggest concern on trade is with Colombia. NAFTA exists," Mr. Bush said, saying the pact was mutually beneficial to the United States as well both of its North American neighbors.
Both Calderon and Harper echoed Mr. Bush's comments on standing by the agreement and not reopening it.
"We agreed that this is not the time to even think about amending it or canceling it. This is the time to strengthen and reinvigorate it," the Mexican president said.
"Jobs have grown in all three" countries as a result of NAFTA, Calderon said. "The benefits are visible."
Calderon said he was respectful of the domestic politics of the United States and that "it is not my role" to talk to any of the presidential candidates about NAFTA. But he made clear that he wants Clinton and Obama to keep their hands off NAFTA.
"To talk about taking a step backwards in terms of free trade, in the case of Mexico, would effectively provoke considerable damage on the economy," Calderon said. Further, he said, that "It would be a sudden loss of economic opportunities that would even lead to even greater migratory pressure against the United States."
Harper said NAFTA was "important for jobs and posterity on both sides of the border."
He said it would be a mistake to renegotiate the agreement, but that Canada would be willing to take part in revisiting the agreement if the other partners insisted.
The Canadian president also said the pact and other economic agreements help to keep energy flowing smoothly. "Canada is the biggest and most stable supplier of energy in the world," he said.
On the pending Colombian trade pact, Mr. Bush singled out Pelosi, saying if she doesn't schedule a vote on Colombia, she will have killed it.
"She's going to have to explain why the voices of false populism have been strengthened," Mr. Bush said, referring to leftist Latin American leaders like Venezuela's President Hugo Chavez.
Layoffs in U.S. manufacturing and the current economic slowdown have made NAFTA and other free-trade deals the subject of intense criticism in the Democratic-led Congress. Both Obama and Clinton want to renegotiate it to add labor and environmental protections.
"I'm concerned about protectionism in America. It is not in our interest to become a projectionist nation," Mr. Bush said.
Earlier, Mr. Bush shared green onion omelets, grits and sides of Canadian bacon with the neighboring leaders on the last day of a summit showing solidarity on cross-border trade.
They ate the family style breakfast at Dooky Chase's Restaurant which was flooded by four feet of water during Hurricane Katrina. The establishment, a gathering place for black musicians and politicians in the 1960s, is owned by Leah Chase, known as the "Queen of Creole Cuisine."