* U.S. corn harvest 7% complete, soy 3%; ratings decline -USDA

* USDA confirms sales of 136,000 T of U.S. soybeans to China

* IKAR raises Russian 2022 wheat crop forecast by 2 mln tonnes

Sept 20 (Reuters) - U.S. grain futures edged higher in Asian trading on Tuesday, with soybeans extending gains on Chinese export demand, while corn rose after a U.S. Department of Agriculture (USDA) report showed a slower-than-expected harvest.

Trading was muted, however, ahead of a series of central bank meetings this week.

The U.S. dollar remained firmly below a two-decade high versus major peers, while world stock markets remained on edge as investors braced for the U.S. Federal Reserve to maintain its aggressive tightening path to contain stubbornly high inflation.

The Fed is likely to raise interest rates by 75 basis points.

The most-traded soybean contract on the Chicago Board of Trade was up 0.2% at $14.64-1/2 a bushel, as of 0208 GMT.

CBOT soybeans rose in the previous session as the USDA confirmed U.S. exporters had sold 136,000 tonnes of the oilseed to China.

"Imported soybeans were insufficient (in China). Oil mills were more willing to support prices," Huatai Futures analysts said in a note.

Tight global supply will also continue to support U.S. soybeans prices, they said.

Top buyer China's soybean imports fell 24.5% in August from a year earlier. Arrivals from No. 2 supplier the United States rose, while imports from Brazil plunged.

CBOT corn rose 0.3% to $6.80 a bushel. The U.S. corn harvest was 7% complete, as of Sunday, the USDA said, below analysts' average estimate of 10% in a Reuters poll.

The U.S. soy harvest was 3% complete, lagging estimates of 5%. Condition ratings for both soybean and corn crops declined, the USDA said.

CBOT wheat rose 0.1% to $8.31-1/4 a bushel in choppy trade. The USDA said 21% of the U.S. crop had been seeded as of Sunday, ahead of estimates of 20% and the five-year average of 17%.

Wheat prices fell in the previous session after Russian agriculture consultancy IKAR raised its forecast for top exporter Russia's 2022 crop by 2 million tonnes. (Reporting by Enrico Dela Cruz in Manila; Editing by Sherry Jacob-Phillips and Devika Syamnath)