BASEL, Switzerland — China National Chemical agreed to buy Swiss pesticide and seeds maker Syngenta for more than $43 billion in cash as the state-backed company extends its shopping spree with what would be the biggest acquisition by a Chinese firm.

ChemChina, as the closely-held company is known, offered $465 a share in cash, according to a statement Wednesday. The offer, endorsed by Syngenta’s board, is about 20 percent higher than the stock’s last close.

Syngenta shares rose 3.8 percent to 407 Swiss francs ($402) at 3:49 p.m. in Zurich, remaining below the offer price amid concern the takeover could be delayed by U.S. regulators.

“Political headwinds, in particular from the U.S., could make the takeover process more lengthy than initially expected,” Ute Haibach, analyst at J. Safra Sarasin, wrote in a note. “The Committee for Foreign Investment in the U.S. will likely watch the transaction closely as China’s domestic seed market is broadly closed to U.S. companies.”

If completed, the deal would help Chairman Ren Jianxin transform ChemChina into the world’s biggest supplier of pesticides and agrochemicals, while snatching an asset coveted by St. Louis-based Monsanto Co. It also underscores the importance China attaches to owning seed and cropcare technology that can boost agricultural output and help feed the world’s biggest population.

The deal is expected to close by year’s end, with a special dividend of 5 Swiss francs a share to be paid if the deal closes. ChemChina plans to keep Syngenta’s management, with Ren chairing a 10-person board that will include four of the existing Syngenta board members. ChemChina will also evaluate a possible initial public offering for the business “in the years to come,” it said.

Deal breakup fees are about $3 billion for ChemChina and $1.5 billion for Syngenta.

Syngenta had sales of $13.4 billion in 2015, mainly from crop protection such such as pesticides and the seeds business. Bolstering agrochemicals would help ChemChina reduce its reliance on petrochemical and petroleum products, which accounted for almost half of the 256.4 billion yuan ($39 billion) in revenue it had in 2014, the latest annual figures available for the company.

Behind the Chinese company’s pursuit are national interests. Chinese President Xi Jinping is trying to boost agricultural output to maintain self-sufficiency as a growing middle class consumes more grain-intensive meat and farmland is converted to housing and golf courses. The World Bank estimates China’s arable land declined 6 percent in the last decade as economic growth boomed.

“We will help the Chinese government to learn,” Chief Executive Officer John Ramsay said in a phone interview. There’s a lot of potential to “improve the quality and technology for Chinese farmers,” he said.

As well as domination of the Chinese market, Syngenta will provide global access to farmers from Brazil to the U.K. Helping execute that vision is Ren, a 58-year-old executive who started China’s first professional cleaning company with a 10,000 yuan loan and is now emerging as one of the country’s most active dealmakers.

Syngenta would trump all past deals in a country whose appetite for foreign assets is surging. ChemChina’s latest purchase follows other Chinese overseas transactions this year including Haier Group Corp.’s $5.4 billion purchase of General Electric Co.’s home-appliance business to Dalian Wanda Group Co.’s deal to buy control of Legendary Entertainment. This year’s tally is on pace to exceed 2015’s record $123.9 billion, according to data compiled by Bloomberg.

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