* Wheat loses momentum on Russian rain forecasts

* Corn pressured by lower wheat prices

* Soy down on technical trading and fast planting progress

CHICAGO, May 29 (Reuters) - Chicago wheat futures edged down on Wednesday as investors took profits after the recent rally and questions remained about whether forecasts for rain in Russia would stem a decline in harvest prospects in the world's biggest exporter.

"The rain in the forecast is taking the edge off the wheat market," said Brian Hoops, president of Midwest Market Solutions.

But traders said the ongoing concerns about the Russia crop's woes may have run out of steam for further pushing wheat prices higher ahead of the U.S. harvest, Hoops said.

Analysts have cut Russian wheat harvest estimates by around 10 million metric tons this month due to persistent dryness and bitter spring frosts.

Weather charts suggest that rain this week could reach part of southern Russia and Ukraine, though analysts remain unsure whether the moisture will significantly improve the crop.

The most-active wheat contract on the Chicago Board of Trade (CBOT) settled down 7-1/2 cents at $6.92-3/4, falling from a 10-month high hit during the previous session.

Meanwhile, soybean and corn futures dipped on technical trading and the U.S. Department of Agriculture's Tuesday report showing speedy planting progress in the U.S. Midwest.

CBOT soybeans settled down 15-1/2 cents at $12.14 per bushel and corn settled 7-1/4 cents lower at $4.55-1/4 a bushel.

The USDA's weekly crop report showed corn and soybean planting was slightly ahead of the average pace of the past five years, at 83% and 68% complete, respectively.

Improved U.S. planting weather and the strong crop progress reports put bearish pressure on corn and soy prices while slipping wheat prices weighed on the grains market.

"Planting continues to roll on despite wetness, which is weighing on prices," said Lane Akre, commodities economist at Pro Farmer. (Reporting by Heather Schlitz in Chicago. Additional reporting by Gus Trompiz in Paris and Peter Hobson in Canberra; Editing by Sherry Jacob-Phillips, Varun H K, Jane Merriman, Alan Barona and Richard Chang)