CHICAGO, June 9 (Reuters) - The U.S. government raised its domestic supply outlook for corn and soybeans on Friday due to waning export demand for both commodities.

A massive harvest in Brazil has cut into overseas demand for U.S. corn and soybeans as buyers on the export market look to the South American country for cheaper supplies of both crops.

"We've had negative export sales. Everything is basically going to South America," said Tomm Pfitzenmaier, analyst for Summit Commodity Brokerage.

U.S. wheat is also struggling to compete on the export market, with Russia dominating as it is able to provide cheap supplies despite the war with Ukraine.

U.S. corn stocks for the 2022/23 marketing year that ends on Aug. 31 were seen at 1.452 billion bushels, the U.S. Agriculture Department (USDA) said in its monthly World Agricultural Supply and Demand Estimates report. Soybean end stocks for 2022/23 were pegged at 230 million bushels.

That compares with May forecasts of 1.417 billion bushels of corn and 215 million bushels of soybeans.

For the 2023/24 marketing year, USDA raised its corn stocks forecast to 2.257 billion bushels from 2.222 billion and its soybean stocks forecast to 350 million from 335 million bushels.

Domestic ending stocks of wheat for the 2022/23 marketing year were pegged at 598 million bushels and at 562 million bushels for the 2023/24 marketing year, higher than last month but still a 16-year low. USDA bumped up its total wheat production forecast for 2023/24 to 1.665 billion bushels from 1.659 billion bushels.

USDA left its outlook for the 2023/24 U.S. corn and soybean harvests unchanged, as it typically does in the June report. Adjustments could be made in the July report. Market reaction was muted.

Brazil's soybean harvest outlook was raised to 156.00 million metric tons and its corn harvest view to 132.00 million metric tons. If realized, both would be records for the world's largest soy and corn exporter.

U.S. corn exports for 2022/23 were seen at 1.725 billion bushels, down from the previous outlook for 1.775 billion bushels. For soybean exports, the 2022/23 projection was lowered to 2.000 billion bushels from 2.015 billion bushels. (Additional reporting by Tom Polansek; Editing by Kirsten Donovan)