Adds closing prices and analyst comments

By Tom Polansek

CHICAGO, May 20 (Reuters) - U.S. corn and soybean futures fell on Wednesday, with traders saying pressure from lower oil prices and favorable U.S. crop weather led the market to retrace gains from early this week that were driven by hopes for increased Chinese buying.

Traders focused on the weather and oil market while waiting for information on which commodities would be affected by potential Chinese purchases of U.S. farm goods.

Rains have boosted soil moisture in the Midwest, favoring early germination of crops, forecaster Vaisala said. Oil prices, meanwhile, fell about 6% after U.S. President Donald Trump said negotiations with Iran were in the final stages.

"Corn was annihilated today on lack of confirmation of Chinese interest, talk of an Iranian war settlement, chart selling, and good weather selling," said Charlie Sernatinger, executive vice president of Marex Capital Markets, in a note.

Chicago Board of Trade July corn futures CN26 ended 9-1/2 cents lower at $4.65-3/4 per bushel and July soybeans SN26 closed down 9-3/4 cents at $11.99-3/4 per bushel. Wheat futures also weakened, with the July contract WN26 finishing down 6-3/4 cents at $6.60-1/2 per bushel.

The markets rallied on Monday after the White House said on Sunday that China committed to purchasing at least $17 billion of U.S. agricultural products in 2026, 2027 and 2028.

Traders were "already getting tired of waiting for a Chinese confirmation that the supposed $17 billion deal would contain corn," Sernatinger said.

China had committed to buying U.S. farm goods during meetings between Trump and Chinese President Xi Jinping last week, according to the White House.

Beijing and Washington agreed to cut tariffs on agricultural trade as part of a broader trade deal, China's Ministry of Commerce said in a statement that left several questions about implementation unanswered.

"While the meeting in China didn't mention more beans being sold, the market perceived the meeting as bullish," said Matt Bennett, CEO of AgMarket.Net, in a note.

China's soybean imports from the U.S. in April more than doubled from a year earlier, as cargoes booked after Beijing resumed purchases late last year gradually arrived at Chinese ports.