CANBERRA, March 21 (Reuters) - Australia's exports of live cattle are likely to rise by more than one-third this year, and beef shipments should increase by 9% as the end of a herd rebuild boosts supply, the U.S. Department of Agriculture (USDA) forecast this week.

Australia is one of the world's biggest agricultural exporters; the country ships live cattle worth about $1 billion and beef worth about $7 billion each year to markets, mostly in Asia.

Exports fell sharply in 2021 and 2022 as wet weather allowed farmers to rebuild their herds after a long dry spell that shrivelled pastures, but began to recover last year.

The United States, a key competitor to Australia in beef markets, has been increasing imports and reducing exports after a long period of destocking that has pushed cattle numbers to their lowest since 1951.

Australia will export 850,000 cattle this year, up from about 626,000 in 2023 and a four-year high, and 1.705 million metric tons of beef and veal, up from 1.562 million tons in 2023, the USDA estimated in a report dated March 19.

The biggest markets for Australian live cattle are Indonesia and Vietnam. The largest for beef are China, the United States, Japan and South Korea.

"With a greater supply of livestock, after reaching the end of the herd rebuild phase, along with moderate live export cattle prices, live cattle exports are set for a big boost in 2024," the USDA said.

"The expected rise in Australian beef exports supports a likely rise in demand for beef imports by the United States and creates an opportunity to regain the market share it lost in recent years during the herd rebuild to its key markets, China, Japan, and South Korea," it said. (Reporting by Peter Hobson. Editing by Gerry Doyle)