Syngenta AG, which has agreed to be taken over by China National Chemical Corp for $43 billion, said talks with US regulatory authorities to win approval for the deal have been constructive and the Swiss company is confident the transaction can be closed on time.

Talks with the Committee on Foreign Investment (CFIUS) in the US are ongoing and the goal remains to complete the deal by year end, CEO Erik Fyrwald said in a phone interview on Friday with Bloomberg News.

Political developments surrounding the forthcoming US election are a "completely separate issue" to the CFIUS review, Fyrwald said. Accepting the Republican Party's nomination on Thursday, Donald Trump accused China of manipulating its currency to distort trade, and vowed to renegotiate trade deals with the nation should he win.

Basel, Switzerland-based Syngenta on Friday reported a 12 percent decline in first-half earnings before interest, taxes, depreciation and amortization to $1.77 billion, lower than an average of $1.91 billion predicted by analysts surveyed by Bloomberg. Sales fell 7 percent to $7.1 billion.

ChemChina's bid values Syngenta at about 20 percent above the closing stock price on Thursday.

ChemChina is seeking regulatory approval for the purchase that will make it the world's largest supplier of pesticides and other crop-care chemicals, albeit temporarily. Dow Chemical Co's merger with DuPont Co and Bayer AG's possible purchase of Monsanto Co will reorder the rankings as the top six suppliers jostle for market share and financial power to drive research and new product releases.

ChemChina recently bought out its Israeli partner in generic agrochemical maker Adama, though the Syngenta CEO doesn't see that as a prelude to combining the companies as they are separate investments.

"I've gotten to know ChemChina through the years, and have great respect for them," Fyrwald said in the interview. "They are long term investors, and that will be the case here."