By Ludwig Burger

(Reuters) - Syngenta, the world's largest pesticides maker being taken over by state-owned ChemChina, still expects the deal to close this year despite concerns that U.S. regulators could throw a spanner in the works, it said on Friday.

The Swiss company's shares slipped after it reported a worse-than-expected drop in first-half profit on Friday, adding to a heavy discount with ChemChina's agreed offer price.

"We are having constructive discussions with all regulatory authorities which reinforce our confidence in closing the transaction by the end of the year," new Chief Executive Erik Fyrwald said in Syngenta's results statement.

Syngenta shares were down 0.2 percent at 387 Swiss francs after the pesticides and seeds maker said first-half net profit fell 13 percent, hurt by weak agricultural markets, a rainy summer in Europe that kept farmers from spraying and a continued decline in sales in Latin America.

The share price is well below ChemChina's offer of $465 (458 Swiss francs) per share, plus a 5 franc special dividend - worth a combined 463 francs - and currently dangles an almost 20 percent gain in front of shareholders.

However, there are persistent concerns in financial markets that the deal could yet be scuppered by the Committee on Foreign Investment in the United States (CFIUS). Syngenta derives about a quarter of its sales from North America.

Syngenta finance chief John Ramsay said the current share price discount to the offer price reflected investor uncertainty about what stance CFIUS will take.

"It's largely due to the fact that CFIUS is an opaque process," he told Reuters. "I think arbitragers typically go out into the market, they listen to the chatter, they take a position. The challenge for everybody is that CFIUS is very tight, very private. They do their job professionally but they don't go leaking information."

Liberum analyst Sophie Jourdier expects the deal to go through and has a 'buy' rating on Syngenta, justified by the wide discount between the current share price and the offer price.

Syngenta reported group net income declined 13 percent to $1.06 billion in the first half from a year earlier, below a Reuters poll forecast of $1.28 billion.

Sales fell 7 percent to $7.09 billion, lagging the market forecast of $7.22 billion.

In the second half, the group expects a return to growth in Asia Pacific as droughts there ease. Growers in Brazil continued to face economic uncertainty and credit constraints.

The group lowered its margin target for earnings before interest, taxes, depreciation and amortization (EBITDA) over sales to flat, from a previous forecast of a margin improvement on last year.

"Group sales for the year are expected to be slightly below last year at constant exchange rates; reported sales are likely to show a mid-single digit decline due to the continuing strength of the dollar," CEO Fyrwald said.

Efficiency measures, lower raw material costs and currency hedging should allow Syngenta to keep its full-year EBITDA margin at around last year's level, he said.

(Additional reporting by Paul Arnold; Editing by Michael Shields and Susan Fenton)