CHICAGO, Sept 25 (Reuters) - Chicago Board of Trade corn and soybean futures rose on Friday, bouncing back from four straight days of declines on a mild round of bargain buying, traders said.

But wheat futures weakened, weighed down by a firm dollar, which makes U.S. supplies more expensive to overseas buyers.

Soybeans fell 4.1% this week, their biggest weekly decline since mid-March, while corn's weekly loss of 3.6% was set to be its biggest since early April.

The declines caused some investors to square positions ahead of the weekend although the gains were muted by expectations of a pick-up in the harvest pace in the coming days.

"You are seeing a little bit of evening up," said Jim Gerlach, president of A/C Trading. "I'll be surprised if they can keep it up because it is going to be a big harvest weekend."

Chicago Board of Trade November soybean futures ended up 2-1/2 cents at $10.02-1/2 a bushel. CBOT December corn was 1-3/4 cents higher at $3.65-1/4 a bushel.

Traders expect market pressure in the coming days as harvesting speeds up and growers book sales directly off their combines, which will cause commercial dealers to hedge those cash purchases of corn and soybeans with shorts in the futures market.

"We are going to have a good weather weekend for harvest, and farmers are expected to respond with plenty of slicing and dicing, and plenty of selling," said Charlie Sernatinger, global head of grain futures at ED&F Man Capital.

CBOT December wheat was off 5-1/2 cents at $5.44-1/4 a bushel. Wheat fell 5.4% this week.

The dollar extended its gains on Friday and was on track for its biggest weekly gain since early April. (Additional reporting by Gus Trompiz in Paris and Naveen Thukral in Singapore; Editing by Mark Potter and Steve Orlofsky)