Alcoa Inc said Wednesday it expects Chinese exports of semi-finished aluminum to slow as prices drop and Beijing increases oversight, even as the U.S. company blamed the world's top producer and consumer for a ballooning global surplus.

Chief Executive Officer Klaus Kleinfeld said shipments of semis, including profiles and plates used to make window frames and beer cans, will likely drop as prices in the international market fall. He also said he believes Beijing is prepared to deal with the export surge, which is not in line with government policy.

Producers, including Alcoa and Rusal, have recently blasted China's swelling exports as a factor behind plunging primary aluminum prices.

Alcoa on Wednesday doubled its forecast for the aluminum surplus this year, as China has not cut output as much as expected.

Asked if he was considering launching a trade case against China, Kleinfeld said the company was considering all options.

"But at this point in time, I'm relatively optimistic that the Chinese will take care of it," he said in a conference call to discuss lower-than-expected second-quarter earnings.

Kleinfeld said Chinese officials made clear to him when he traveled to Beijing four weeks ago that the rise in exports was not part of their policy and that they were looking into the issue, he said.

Kleinfeld calls China's semis shipments "fake" because they are produced and shipped to avoid an export tax on primary aluminum, only to be re-melted into primary aluminum by the end user.

Supply will outpace global demand by 760,000 tonnes this year, some 400,000 tonnes higher than its previous forecast, Alcoa Chief Financial Officer William Oplinger said on the call.

"This is largely driven by the lack of follow through on curtailments on unprofitable operating capacity even with the recent pressure on metal prices," he said.

Oversupply in China will be 2.2 million tonnes this year, up from 1.8 million tonnes previously, he said.