SINGAPORE: Chicago wheat futures rose for a fifth consecutive session on Friday and were set their biggest weekly gain in four months, as concerns about tight exportable global surplus kept prices near their highest in nine years.

Soybeans and corn gained ground and both markets were on track to finish the week in positive territory.

The most-active wheat contract on the Chicago Board Of Trade (CBOT) rose 0.4% to $8.16 a bushel by 0252 GMT. It closed 1.2% firmer on Thursday, when prices hit their highest since December 2012.

Wheat has gained 6.5% so far in the week.

Soybeans have added 1.7% for the week after closing down 3.5% in the previous week, while corn is up 3.3% this week after a 2.7% drop in the previous week.

Support for the wheat market also stemmed from the prospect that Russia, the world's top supplier, could curb exports.

The country may change the way it calculates grain export taxes if prices rise further, Agriculture Minister Dmitry Patrushev said.

Russia also plans to set export quotas for the first half of 2022.

Brazil cleared imports of flour from Argentina made with genetically modified wheat, although shipments of the new variety are unlikely anytime soon given uncertainty about broader global acceptance and opposition from a powerful wheat millers' lobby.

The market is still digesting the US Department of Agriculture's surprise cut this week to its estimate of the US soybean yield. But rallies were capped by rising expectations of a massive Brazilian soy harvest.

Brazilian government supply agency Conab raised its forecast of the country's 2021/22 soybean harvest to 142.0 million tonnes from 140.8 million previously.

Trade group Abiove projected Brazil's soybean crop at a record 144.1 million tonnes and said output could be higher, depending on weather.

Commodity funds were net buyers of CBOT wheat, corn, soybean and soymeal futures contracts on Thursday, traders said. They were net even for the day in soyoil.