* Valero aims to sell 40 million shares at $18 each

* Offer to close June 9

LOS ANGELES, June 3 (Reuters) - Top U.S. refiner Valero Energy Corp (VLO.N: Quote, Profile, Research) plans to raise $720 million through a share sale this month to bolster its capital spending plans and bankroll acquisitions.

Valero, an erstwhile industry and investor darling until a recent surge in the price of sour crude crimped its margins, said on Wednesday it had priced an offering of 40 million common shares at $18 apiece. [ID:nWNAB6424]

The company also granted underwriters Barclays (BARC.L: Quote, Profile, Research) Capital and JPMorgan (JPM.N: Quote, Profile, Research) Securities Inc an option to buy an additional 6 million shares of common stock.

On Tuesday, Valero posted a second-quarter loss that it blamed on weak market conditions and the indefinite delay of two pivotal expansion projects. [ID:nN02393895]

Sour crude, which contains a high sulfur content, has been key to refiners' profits since 2002 because it was less costly than other crude oil grades. But this year, sour crudes have seen their cost advantage largely disappear, hitting the bottom line for refiners from Tesoro (TSO.N: Quote, Profile, Research) to Western Refining Inc (WNR.N: Quote, Profile, Research).

Now, Valero -- which went on a buying binge in 2009 to expand capacity -- hopes to raise cash to fund a $2.5 billion spending plan for 2009 as well as finance "recently completed and pending acquisitions".

Last month, it announced plans to buy Dow Chemical Co's stake in a Dutch refinery for $725 million. It also bought a smattering of bankrupt VeraSun's ethanol plants for $477 million.