WASHINGTON — Not every part of the nation's economy is sagging, despite all the grim news: Exports are surging.

As the falling dollar has made U.S. products more affordable abroad, foreigners have been snapping up American aircraft, machinery, agricultural goods and other products at what amount to bargain rates. And that has resulted in a 5.5 percent annual rate of increase in exports in the first quarter of the year.

Although that pace is behind the red-hot rates of the past two years, it has been critical in preventing the nation's economic slowdown from slipping into negative-growth territory. The economy grew 0.6 percent in the first three months of the year, even as some sectors slowed sharply.

But some analysts said the boom that caused U.S. exports to grow by an inflation-adjusted 17 percent from 2005 to 2007 may not be sustainable as countries across the world feel the pinch of the credit crisis and spiraling food and energy prices.

"What the U.S. faces in terms of difficult credit and food and energy inflation are global problems," said Steven Wieting, chief U.S. economist for Citigroup. While U.S. trade performance is likely to continue to be strong, he said, "we may have seen the absolute peak growth rates."

Many firms have shared in the growth. "We are effervescent," said Drew Greenblatt, owner of Marlin Steel Wire Products, a Baltimore firm that designs and makes custom wire baskets used by dozens of firms around the world, including Toyota and Pfizer. "There is a lot of chatter out there about how poorly the economy is doing, but we're not seeing it."

He said Marlin, which had sales of $3 million in 2007, has grown 18 percent since the first quarter of last year, and he expects more of the same in the coming months. Much of that is because of exports, which have grown from almost nothing to 10 percent of the company's business in the past two years. "There are people here putting food on their tables because of the increase in global trade," he said.

Foreign tourism has been another bright spot in the U.S. economy, again in large part because of the strength of the euro against the dollar.

In January, 3.4 million international visitors came to the United States, an 11 percent increase over the previous January, according to the Commerce Department. Hotel occupancy and attendance at Broadway plays were up in New York, and businesses in cities including Atlanta, Minneapolis and Kansas City reported strong tourism demand, according the Federal Reserve's latest "beige book," a report based on interviews with business leaders across the country. That increase in tourism came after a record-setting 2007, when 56 million foreign tourists spent an estimated $122 billion in the United States.

With commodity and energy prices at a high point, wheat, corn and soybean farmers and steel producers are experiencing good times, economists said. "Steel products have been pretty strong over the past year or so," said Tim Dunne, senior economic adviser to the Federal Reserve Bank of Cleveland.

With the dollar weakened and energy prices high, many firms have less interest in imported steel. In addition, supply is tight, allowing steel mills to demand their price. "There is no question the industry is doing very well," said Dick McLaughlin, managing director of Hatch Beddows, a consulting firm.

Even as exports and foreign tourism help fuel the otherwise anemic U.S. economy, the public is taking a much more critical view of free-trade agreements, which are aimed at further integrating the nation's economy with that of the rest of the world.

Nearly half of Americans say such agreements are bad for the country, the highest proportion since the question was first asked in 1997, according to an April survey by the Pew Research Center. There is now a broad agreement that free trade hurts wages, jobs and economic growth in America, the poll found.

Dave Huether, chief economist for the National Association of Manufacturers, called the hardening opposition to free trade misguided — especially at a time when exports were playing a key role in keeping the economy afloat. While he said export growth could be headed for a patch during which it is not as strong as it has been in recent past, he said the forecast is still for solid growth, making exports a "silver lining" in an otherwise gloomy economic outlook.