LIMA, July 2 (Reuters) - Peru's May trade surplus widened 40 percent from the same month a year ago to $634 million, the Andean country's largest surplus so far this year, the central bank said on Thursday.

The bank said the value of traditional exports such as metals rose, while all categories of imports fell in May compared with the previous month.

In May, exports totaled $2.11 billion while imports were valued at $1.48 billion.

May's result was the fourth straight month of surpluses after Peru posted a January trade deficit. In May 2008, the country posted a $451.5 million surplus.

Prices for most of Peru's metal exports, which are the government's largest source of revenue, plummeted on the global economic slowdown but have recently begun to rise.

Peru's economy is expected to expand 3.5 percent this year, easing from a blistering 10 percent growth rate in 2008.

Last year, Peru's trade surplus shrank more than 60 percent to $3.09 billion from $8.29 billion in 2007.

(Reporting by Dana Ford; Editing by Theodore d'Afflisio) Keywords: PERU ECONOMY/TRADE

(dana.ford@thomsonreuters.com; +511 221-2130; Reuters Messaging: dana.ford.reuters.com@reuters.net)

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