GRAINS-Corn extends gains on US supply doubts

PARIS/CANBERRA, Oct 17 (Reuters) - Chicago corn futures extended gains into a fourth session on Friday and were set for a first weekly rise in a month as participants assessed reports of lower than expected U.S. harvest yields amid a lack of government data.

Soybeans rose for a third day, also underpinned by brisk domestic demand that has tempered worries over U.S.-China tensions that have halted soybean trade between the two countries.

Wheat tracked corn higher as it recovered from a five-year low this week.

The most-active corn contract on the Chicago Board of Trade (CBOT) Cv1 was up 0.6% at $4.24-1/4 a bushel at 1149 GMT, extending its recovery from a seven-week low struck on Tuesday.

Over the week, it was up 2.7%, on course to break a run of four weekly losses.

The ongoing U.S. corn harvest is widely forecast to set a production record. But with the U.S. Department of Agriculture postponing most crop data due to a government shutdown, traders have been focusing on signs that some yields are below previous expectations.

"Indications are coming in a bit disappointing here and there," said Tobin Gorey, founder of Australian consultant Cornucopia. "There's speculation that we saw peak yield numbers a while ago and it's come back a bit."

Traders have also said farmers' reluctance to sell has tightened new-crop supply of corn and soybeans.

Global grain merchant ADM ADM.N is offering incentives for U.S. farmers to deliver soybeans to a major processing facility this month, sources said.

The soybean market also drew support from stronger than expected U.S. soy crushing for September reported this week.

That took the focus off the dearth of Chinese demand, though lagging exports remained a burden on the oilseed market, traders said.

CBOT soybeans Sv1 added 0.5% to $10.15-3/4 a bushel, while CBOT wheat Wv1 was 0.4% higher at $5.04-1/4 a bushel.

Wheat set five-year lows in the past week as global export competition was set to intensify with bumper harvests expected soon in Argentina and Australia.

Western Australia will produce nearly 1 million metric tons more wheat this season than was expected a month ago, an industry group said on Friday.

However, in Argentina, a cold front forecast over the agricultural heartlands next week could affect wheat yields, the Buenos Aires grains exchange said on Thursday.