Asian stocks swung between gains and losses and the euro rose as investors awaited a policy announcement from the European Central Bank after the Federal Reserve pledged more support for the U.S. economy if necessary. Corn rallied.

The MSCI Asia Pacific Index (MXAP) fell less than 0.1 percent as of 1:52 p.m. in Tokyo after rising 0.1 percent and slipping as much as 0.3 percent. Japan’s Topix Index climbed 0.8 percent on improved earnings. Standard & Poor’s 500 Index futures added 0.2 percent. The euro traded for $1.225, up 0.2 percent, while South Korea’s won weakened from a four-month high. Corn advanced for the first time in three days.

ECB President Mario Draghi’s pledge last week to do “whatever it takes” to preserve the euro raised expectations for today’s policy decision. The Fed signaled its readiness to support the economy even as it refrained from adding to bond purchases yesterday. Asia’s benchmark MSCI Asia Pacific gauge fell for a second day after recording its biggest four-day gain this year through July 31

“Investors are being cautious, taking into account the possibility of their expectations being betrayed,” said Ayako Sera, a market strategist at Sumitomo Mitsui Trust Bank Ltd., which has 33 trillion yen ($420 billion) in assets. “Asian markets are hoping but not completely believing that the ECB will do more.”

The MSCI Asia Pacific Index advanced 5.1 percent in the four trading days through July 31, the biggest such increase since December. Most investors expect the ECB will buy government bonds to Spain and Italy, Goldman Sachs Group Inc. said in a note yesterday, citing a survey of 410 people.

Euro, Ringgit

The euro rose against most of its major counterparts after declining yesterday. South Korea’s won dropped 0.2 percent against the dollar, while the Malaysian ringgit retreated 0.4 percent from a two-month high versus the greenback after the Fed chose not to buy more bonds. Australia’s dollar climbed 0.2 percent after the country’s retail sales increased more than economists expected.

Oil for September delivery was at $88.82 a barrel in electronic trading on the New York Mercantile Exchange. The contract yesterday rose 85 cents, or 1 percent, the biggest gain in almost two weeks after stockpiles declined the most in seven months in the U.S., the world’s biggest crude consumer. Prices are 10 percent lower this year.

Corn’s December-delivery contract climbed as much as 1 percent to $8.0825 a bushel on the Chicago Board of Trade. A persistent drought in the U.S Midwest increased speculation that the Department of Agriculture will lower its estimate of the nation’s harvest.

To contact the reporters on this story: Jason Clenfield in Tokyo at jclenfield@bloomberg.net; Kana Nishizawa in Hong Kong at knishizawa5@bloomberg.net

To contact the editor responsible for this story: Nick Gentle at ngentle2@bloomberg.net