GRAINS-Soybeans extend slide as Argentina competition and stalled China demand weigh

By Gus Trompiz and Naveen Thukral

PARIS/SINGAPORE, Sept 23 (Reuters) - Chicago soybeans lost more ground on Tuesday to hit a six-week low, pressured by a lack of Chinese demand for U.S. supplies and the prospect of increased competition from Argentina after the country waived grain export duties.

Wheat edged down to set new contract lows, with an expected boost to Argentine exports also weighing on the cereal market amid ample global supply.

Corn was flat, with brisk U.S. exports and uncertainty over U.S. yields countering broad supply pressure.

The most active soybean contract on the Chicago Board of Trade Sv1 was down 0.4% at $10.07-1/2 a bushel by 1132 GMT, heading for a fifth straight daily loss.

It earlier hit its lowest since August 12 at $10.05, but held the psychological $10 floor.

Argentina on Monday temporarily eliminated export taxes on grains and their by-products, as well as on beef and poultry, in a bid to speed up sales abroad and rake in much-needed dollars to prop up the flagging peso.

That prompted Chinese buyers to book at least 10 cargoes of Argentine soybeans, traders told Reuters, reinforcing China's shift towards South American supply as it shuns U.S. soy during a trade dispute with Washington.

"China is the key U.S. beans buyer. Soy weakness is bleeding into all ags," said Andrey Sizov, head of consultancy Sovecon.

"The temporary Argentina taxes elimination put additional pressure on the market. Soy was hit the hardest again," he said.

Hopes of a resumption in U.S. soybean trade with China were dashed when a call on Friday between U.S. President Donald Trump and Chinese counterpart Xi Jinping brought no news about agricultural commodities.

Soybeans and corn are also facing seasonal supply pressure from the onset of the U.S. harvest, though doubts over the size of yields have helped underpin the market.

The U.S. corn harvest was 11% complete by Sunday and the soybean harvest was 9%, while condition ratings for both crops declined last week, according to a government report issued after the market closed on Monday.

CBOT corn Cv1 was unchanged on the day at $4.21-3/4 a bushel.

CBOT wheat Wv1 ticked down 0.1% to $5.10-1/2 a bushel after hitting its lowest in almost six weeks at $5.07-1/4. Individual delivery months for wheat set more contract lows.

After tepid international demand this month, traders will be watching the outcome of an Algerian wheat tender on Tuesday to gauge export competition. GRA/TEND