Mosaic Co. plans to plunk $1 billion into a joint venture to mine phosphate and produce fertilizer in Saudi Arabia, a deal that marks the Plymouth-based firm’s largest international investment to date.

Mosaic, the world’s biggest phosphate fertilizer maker, will own a 25 percent interest in the $7 billion Saudi project, slated to begin production in late 2016. Saudi Arabian Mining Co., also known as Ma’aden, will own 60 percent of the venture, and Saudi Basic Industries Corp. will own 15 percent.

In connection with its equity share, Mosaic plans to market 25 percent of the joint venture’s production. Its $1 billion cash investment will be spread over four years.

“This is a sizable investment, and it does make strategic sense for Mosaic,” said Jeffrey Stafford, a stock analyst at Morningstar Inc.

Mosaic is an integrated producer, mining phosphate and potash and then turning it into fertilizer. The company, which was created in 2004 when Cargill merged its fertilizer business with IMC Global, draws the bulk of its phosphate from mines in Florida.

With the Saudi deal, Mosaic will have a phosphate source closer to crucial Asian markets, particularly India, a huge fertilizer importer, Stafford said.

The Saudi venture will serve customers globally, the company says. But “from a freight-rate perspective, Mideast markets are certainly great targets,” said Bo Davis, Mosaic’s senior vice president for phosphate.

Stafford said the Saudi deal also allows Mosaic to diversify its phosphate supply, a need underscored by hurdles the company has faced in Florida in recent years.

The Sierra Club and other environmental groups in 2011 persuaded a federal judge to halt expansion of a big Mosaic mine in Florida, claiming it would damage wetlands. Mosaic and the Sierra Club settled litigation in early 2012, allowing the project to go forward.

Florida will still be, by far, the company’s main source of phosphate. Indeed, Davis said Mosaic plans to invest $2 billion over the next several years in its Florida mines. Mosaic also gets phosphate from a 35 percent stake in a Peruvian phosphate mine.

The new joint venture would be based in Wa’ad Al Shammal Minerals Industrial City in northern Saudi Arabia and also involve expanding an existing plant at Ras Al Khair Minerals Industrial City on the country’s eastern coast. The project would produce 3.5 million metric tons of phosphate fertilizer, animal feed and other products.

The development would essentially mark the second phase of an existing phosphate venture by Saudi Arabia Mining Co. and Saudi Basic Industries. The first phase has a 3 million-ton capacity.

Saudi Arabia has focused on mining as a critical way to diversify its economy beyond oil production. Saudi Arabian Mining, which has interests in gold, bauxite and other minerals, is a publicly traded company controlled by the Kingdom of Saudi Arabia.

The deal is subject to board and government approvals. Mosaic’s stock closed Tuesday at $61.34, down 59 cents.