U.S. exports hit a record high in March, buoyed by the weak dollar and strengthening global demand as U.S. trade returned to levels last seen before the global financial crisis.

U.S. exports grew 4.6 percent in March to $172.7 billion, surpassing the record set in July 2008 before world trade took a sharp downturn. The March export rise was the biggest month-to-month gain in 17 years, the Commerce Department said in a report on Wednesday.

It's taken two-and-a-half years, but the level of exports has finally returned to pre-recession levels, said Paul Dales, senior U.S. economist with Capital Economics in Toronto.

Despite the big gain, the U.S. trade deficit grew to $48.2 billion in the month, the widest since June 2010, as rising oil prices helped push imports nearly 5 percent higher.

The rise in exports will be welcome news for the White House. President Barack Obama has vowed to double U.S. exports in five years and strong growth in the U.S. manufacturing industry, helped by demand from fast-growing emerging economies such as China, has led the economic recovery.

Chris Low, chief economist at FTN Financial, noted U.S. exports have now grown in four of the past five months and are up nearly 15 percent from a year ago.

The closely watched U.S. trade deficit with China narrowed slightly in March to $18.1 billion, as U.S. exports to that country grew faster than imports from the Asian giant.

Economists said the wider-than-expected trade gap in March was unlikely to change significantly estimates of already weak first-quarter U.S. economic growth.

More generally, the latest surveys suggest that export growth will continue to accelerate, with the lower dollar providing further support. But the surveys suggest that imports will continue to grow at a faster rate, Dales said.

Both U.S. goods and U.S. services exports set records in March, as did two sub-categories - foods, feeds and beverages and industrial supplies. U.S. exports to Canada and South and Central America also set records and exports to the European Union were the highest since July 2008.

A weaker dollar helps U.S. exports by making them cheaper in world markets. The dollar has fallen 5.2 percent against a basket of currencies since the start of 2011. Against the euro, the dollar has been down nearly 7 percent so far this year.

Imports grew 4.9 percent to $220.8 billion as the average price for imported oil hit $93.76 per barrel, the highest since September 2008. Oil prices continued to rise in April, but have receded in recent weeks back to early March levels.

Pierre Ellis, senior global economist at Decision Economics in New York, said the trade data could provide ammunition for members of the Federal Reserve board that want to tighten monetary policy to curb the threat of inflation.

This is a reassurance on growth, which is what the hawkish members of the Fed are looking for. This is a piece of evidence for them to consider removing accommodation before things start overheating a couple of years down the road, he said.

U.S. imports were the highest since August 2008, just as the global financial crisis was beginning to bite into trade. Imports hit a record $232.1 billion in July 2008, before tumbling sharply over the next six months.

U.S. petroleum imports were also the highest since August 2008 and the U.S. petroleum trade deficit was the widest since October 2008.

While the U.S. trade deficit with China narrowed in March, the shortfall for the first quarter hit $60.2 billion, putting it on pace to exceed last year's record of around $273 billion.

China's own data this week showed it posted its biggest surplus in four months in April, as exports hit a record on stronger global demand.

U.S. and Chinese officials sparred over China's exchange rate policies during high-level talks this week in Washington.

The United States pressed for a faster rise in the yuan's value to help bring trade into balance, while China said it would continue exchange rate reform at its own pace.

So far, there was little sign of disruption to Japan's exports to the United States after the March 11 earthquake and tsunami that caused widespread damage to the country's manufacturing base, including exporters of goods and parts.

Economists at Wells Fargo said the impact was more likely to be seen in U.S. trade data for April.

Separately, a Labor Department report showed U.S. job openings in March were the most in 2-1/2 years, pointing to a firmer tone in the labor market. Job openings rose 99,000 to 3.12 million, the highest since September 2008.

(Additional reporting by Richard Leong in New York, Editing by Andrea Ricci)