China National Chemical Corp is closing in on a $43 billion deal to buy the Swiss pesticide giant Syngenta (LSE: 0QOP.L - news) , according to reports Tuesday, which would be the biggest-ever acquisition by a Chinese firm.

The deal could be announced as soon as Wednesday -- when Syngenta's results are published -- but it has not yet been finalised, Bloomberg quoted people familiar with the matter as saying.

If it goes ahead, the deal would outstrip the China Unicom Hong Kong Ltd.'s purchase of China Netcom Group Corp. in 2008, according to data from the organisation.

Syngenta declined to comment when contacted by AFP.

An offer would be welcomed by investors "because it is entirely in cash," said an analyst at Germany's Baader Bank (Xetra: 508810 - news) .

However, "it could pose political problems," added the analyst.

Last month, ChemChina said it would buy Germany's KraussMaffei Group, which makes machinery for producing plastics and rubber, for 925 million euros ($1.0 billion).

The state giant also in January announced it had bought a 12 percent stake in Swiss energy and commodities trader Mercuria in a bid to expand its portfolio.