A large open interest in the $5.40 strike level was pulling the underlying market to that level this week, traders said.
By 10:30 am CST (1630 GMT) March soyabeans were 5-1/4 cents higher at $5.40-1/4 per bushel, climbing 11 cents at one point to $5.46. The back months were 5-1/4 to 7 cents higher.
Refco and Rand Financial each bought 300-400 May early. Local traders were featured buyers in options.
The rally in soyabeans was stirring fresh bean sales right off the farm, Midwest processors said.
Some meteorologists had taken rain out of their southern Brazil forecasts for mid next week, which gave the market a lift.
Dryness is increasing stress on the Brazilian soya crop through Rio Grande do Sul, Parana, and southern Mato Grosso, and crop losses are occurring, said Meteorlogix weather service.
Soyameal futures were $1.90 to $3 per ton higher, on spillover support from soyabeans. March meal was up $1.90 at $164.80.
US weekly export sales for soyabean meal were somewhat supportive. USDA said last week's sales were 175,300 tonnes (old-crop and new-crop combined). The 2004/05 tally of 173,500 tonnes was nearly four times higher than the previous week.
The soyaoil market was also higher on a recovery bounce from this week's sell-off linked to a big jump in US soyaoil stocks during January. The early strength in soyabeans was also supportive.
March soyaoil was up 0.11 at 19.67 per lb., with the back months 0.12 higher to down 0.01 cent.