* Wheat headed for a fourth straight weekly gain on dry weather
* Corn up for a 9th week in 10, soybeans firm
* Investors eye USDA quarterly stocks, plantings report on Monday
(Updates prices, comments; changes byline/dateline)
March 28 (Reuters) - U.S. wheat futures eased on Friday as investors awaited key U.S. planting and stocks data, but stayed on course for a weekly rise as dry weather in the U.S. Plains continued to worry the market.
Corn and soybeans inched lower in subdued trading in the run-up to Monday's spring planting and quarterly stocks estimates from the U.S. Department of Agriculture, a data release that often generates sharp price movements.
Wheat gained 3 percent on Monday and another 2 percent on Thursday on concerns that drought will hurt wheat crops in major producing states like Kansas, Oklahoma and Texas, adding to recent support from tensions between major grain exporters Russia and Ukraine.
But forecasts for some rain in parts of the U.S. grain belt and the prospect of large global harvests in 2014 have acted as a brake on wheat prices in the run-up to Monday's USDA numbers.
"There are more-than-adequate supplies of old crop coarse grains, and we see the likelihood of another large global 2014 wheat and corn harvest," David Sheppard, managing director of UK merchant Gleadell, said in a note.
"However, as we have seen over the past few weeks, we should never underestimate the power of politics and the impact of perceived or real weather events."
Wheat for delivery in May on the Chicago Board of Trade was down 0.8 percent at $7.04-1/2 a bushel by 1314 GMT. The contract was still up 1.6 percent over the week.
In addition to concern over U.S. crops, the wheat market got a short-lived lift on Thursday from bigger-than-expected U.S. weekly exports.
But the International Grains Council underlined ample global supply by raising on Thursday its forecast for world wheat production in 2014/15.
Chicago corn was off 0.2 percent at $4.91-1/4 a bushel after hitting a near three-week high of $4.92-3/4 on Thursday on strong U.S. exports. Corn is up 2.4 percent this week, its ninth increase in 10 weeks.
U.S. corn sales last week stood at 1.4 million tonnes, well above analysts' expectations that ranged from 525,000 to 725,000 tonnes, a report from the U.S. Department of Agriculture showed.
Soybeans inched down half a cent to $14.36 per bushel.
U.S. soybean export sales last week reached only 11,900 tonnes, near the marketing-year low hit in mid-February, suggesting tight U.S. stocks may be curbing demand after brisk demand so far this season.
Analysts expect a key USDA report, due on Monday, to show that U.S. soybean stocks by March 1 were 989 million bushels, which would be the smallest since 2004.
U.S. corn stockpiles are seen at 7.099 billion bushels, the biggest since 2010, and wheat stocks at a five-year low of 1.042 billion bushels.
* Prices as of 1314 GMT
Product Last Change Pct Move CBOT wheat 704.50 -6.00 -0.84 CBOT corn 491.25 -0.75 -0.15 CBOT soy 1436.00 -0.50 -0.03 Paris wheat 211.00 -0.50 -0.24 Paris maize 185.50 -0.25 -0.13 Paris rape 411.25 0.25 +0.06 WTI crude oil 101.83 0.55 +0.54 * CBOT futures prices are in cents per bushel, Paris futures in
euros per tonne, WTI crude oil in dollars per barrel.
(Editing by Clarence Fernandez and Muralikumar Anantharaman; editing by Keiron Henderson)