By David Bailey and Ben Klayman

DETROIT (Reuters) - General Motors Corp (GM.N: Quote, Profile, Research) on Wednesday posted a first-quarter decline in global sales after falling in North America, trailing Toyota Motor Corp (7203.T: Quote, Profile, Research) decisively in the period as the world's top automaker.

GM also said second-quarter U.S. auto sales may be weaker for the industry than the first quarter as fuel prices rise. But the automaker still expects a recovery in the second half of 2008 and has seen minimal spread of U.S. economic problems into the rapidly growing emerging markets.

"What we're wondering and asking ourselves is perhaps the second quarter will be weaker than the first quarter," GM Chief Sales Analyst Mike DiGiovanni told analysts and reporters after saying GM has factored a weaker second quarter into its plans.

"That said, we still believe ... the fundamentals are in place for a second-half recovery," DiGiovanni added.

DiGiovanni said April sales may have weakened "a bit" from March, but later said the results have been similar.

GM reported a 0.6 percent decline in global sales to 2.25 million vehicles in the first quarter, falling behind Toyota, which reported sales rose 2.7 percent to 2.41 million vehicles in the January-to-March period.

GM and Toyota were roughly even in 2007 for the top spot among the world's automakers, with GM slightly ahead if sales from a China business were included.

DiGiovanni said GM had anticipated Toyota would outsell it during the first quarter and had outsold the largest U.S. automaker in the first quarter of 2007 as well.