Blackstone has teamed up with China National BlueStar to bid for Nufarm, the Australian agricultural chemicals maker, in a move that underlines the buy-out firm’s strengthening ties with China.

Blackstone and the Chinese chemicals maker, in which it holds a 20 per cent stake, expressed an interest in buying the Australian group last month for about US$2.7bn. The two were rebuffed by Nufarm, but are understood to have forced it back to the negotiating table after indicating that they were willing to make a fresh bid valuing the company at closer to US$4bn.