Eurotunnel carries Eurostar high-speed trains between Paris, Brussels and London, as well as shuttle trains containing passenger cars, coaches and freight trucks.

"We are very calm about our guidance. We continue to do well and to improve our EBITDA and our revenue. At this stage we are very positive and we confirm our 2017 and 2018 goals for profitability and dividends," Chief Executive Jacques Gounon told a conference call on first-half results.

Eurotunnel lost as much as a third of its market value in the immediate aftermath of Britain's vote in favour of Brexit and leaving the European Union back in June 2016, despite offering reassurances that it would not suffer.

Eurotunnel, however, said in a statement that it did not see any significant impact from Brexit on its business in the first-half, although it continued to keep a close eye on the matter.

The International Monetary Fund predicted on Monday that Britain's economy now looked set to grow by 1.7 percent this year, down from a forecast made in April of 2.0 percent. The IMF said its downgrade reflected Britain's weaker-than-expected growth in the early part of this year.

"We are expecting some growth in Britain, albeit not an exceptional growth. Our traffic is holding up and the summer is looking good," Gounon said.

Eurotunnel kept its forecast for earnings before interest, taxes, depreciation and amortisation (EBITDA) of 530 million euros ($618 million) this year and 560 million in 2018. This would compare with EBITDA 2016 of 514 million.

It was also still targeting a dividend of 0.30 euros per share for 2017 and 0.35 euros for 2018.

The 2017 and 2018 forecasts were made on the basis of an exchange rate of 1.175 euros per pound.

The company reported an 8 percent increase in EBITDA for the first half of 2017 to 242 million euros, while first half revenues rose 3 percent.

This was achieved thanks to lower operating costs and a 3.7 percent rise in average prices on the Channel tunnel fixed link, which offset lower lorry and car shuttle traffic.

Eurotunnel said lorry shuttle traffic was down 0.8 percent in the first half of 2017, with 823,147 trucks transported.

Truck traffic at the start of 2017 suffered from a decrease in fruit and vegetable traffic to Britain due to bad weather in southern Europe, and Gounon said the goal of transporting two million trucks by 2020 could be delayed by one year.

Passenger car shuttle traffic fell 2.1 percent during the first half, partly impacted by elections in France and Britain.

However, the number of Eurostar passengers travelling through the Tunnel rose by 1 percent despite militant Islamist attacks in Britain during the first-half of this year.

(Reporting by Dominique Vidalon; Editing by Sudip Kar-Gupta)

By Dominique Vidalon