NAPERVILLE, Illinois, July 20 (Reuters) - Huge Brazilian supplies, high prices and uncertainty about U.S. crops have caused pessimism toward the United States’ corn and soybean export potential into the new marketing year that begins Sept. 1.

The pace of new-crop U.S. corn and soybean export sales usually starts to increase in July and especially into August. That has happened to some degree over the last month, but total bookings for both sit at four-year lows.

Data from the U.S. Department of Agriculture on Thursday showed that as of July 13, U.S. exporters had sold 4.5 million tonnes of corn and 4.9 million tonnes of soybeans for delivery in 2023-24. Those are both the lowest for the date since 2019, ahead of 2019-20.

That covers only 8% of USDA’s 2023-24 U.S. corn export forecast of 53.3 million tonnes (2.1 billion bushels), below the five-year average of 13%. However, that average is skewed upward by the latest three years when China was heavily buying and includes 25% coverage by this date in 2021.

New-crop soybean sales account for 10% of USDA’s 2023-24 export target of 50.35 million tonnes (1.85 billion bushels). The five-year average is 16% and is skewed by last year’s 24% as buyers scrambled to secure U.S. supply amid historic drought-related losses in Brazil.

Both of those export outlooks, especially the one for corn, are considered too optimistic by some analysts since cheaper Brazilian supplies are seen increasingly eating in to U.S. export shares. But for now, focus should be on the U.S. crop since that will determine price direction and ultimately demand.

Although this week’s futures rally would not suggest it, USDA still has a record U.S. corn crop penciled in for this year. That is set to increase overall U.S. corn supplies by 11%, the biggest annual increase in a decade, allowing for healthy but not excessive growth in exports on the balance sheet.

Available U.S. soybean supply is expected to remain flat into 2023-24, but USDA has U.S. exports falling nearly 7% on the year. Also noteworthy is that the agency has 2023-24 Chinese soy imports steady on the year at 99 million tonnes.

WHO'S IN, WHO'S OUT

Corn sales for the new marketing year reached 492,000 tonnes in the week ended July 13, the largest weekly volume of 2023-24 sales since November and slightly higher than in the prior week. Last week’s new-crop bean total of 760,000 tonnes was 2023-24’s best so far.

Last week’s new-crop corn and soy commitments were heavily driven by sales to Mexico, and in fact, total new-crop U.S. corn bookings to Mexico of 2.8 million tonnes are a record for the date. New soy sales to Mexico of 884,000 tonnes is the date’s second-biggest total after 2018.

Mexico is the top U.S. corn buyer and is No. 2 in soybeans, but top soy customer China has been dragging its feet as Brazil’s record soy harvest continues arriving at Chinese ports.

China has purchased 1.87 million tonnes of new-crop U.S. soybeans, the lowest mid-July, non-trade-war-year volume in at least 16 years. Soy sales to unknown destinations, often presumed to be China, are also well below average at 1.6 million tonnes, similar to the same date in 2017.

China’s recent lack of participation in U.S. corn trade is stark but unsurprising given China entered Brazil’s corn market late last year. China has 272,000 tonnes of new-crop U.S. corn booked for 2023-24 compared with nearly 3 million tonnes on the same dates in 2020 and 2022 and 10.7 million in 2021.

No. 3 U.S. corn buyer Japan has purchased 746,000 tonnes of new-crop corn, near the recent average for the date, though standard customers Colombia and South Korea have nothing. Canada has bought nearly 300,000 tonnes of new-crop U.S. corn so far, a record for mid-July. Karen Braun is a market analyst for Reuters. Views expressed above are her own.

(Reporting by Karen Braun Editing by Matthew Lewis)