President of Finland Sauli Niinisto has denied President Donald Trump's remarks that the Finnish armed force was buying a fleet of F-18s from American aircraft maker Boeing.

Trump, while speaking at a news conference with Finnish president Niinisto at the White House on Monday (28 August) had said, "One of the things that is happening is you're purchasing large amounts of our great F-18 aircraft from Boeing and it's one of the great planes, the great fighter jets," hinting that there was a finalised trade deal between Finland and Boeing.

While Niinisto appeared surprised at the statement, he did not follow up on the comment from Trump right away.

Later in the day, he tweeted out a contradiction to Trump's claim by simply calling the news a duck. "The news of the purchase of F-18 fighter planes is a duck," he tweeted in Finnish.

Social media users were quick to explain the president's reference to a "duck" in this context, saying it means "fake news" in Finnish.

Finland is trying to upgrade its fleet of 62 F/A-18 Hornet jets, but there has been no actual deal finalised with any company as yet. The deal, should it go through, will be worth around €7bn to €10bn (£6.48 to £9.26bn) by 2025, reports Reuters.

So far, it is reported that Finland has only asked for quotations from various airplane makers from across the industry, including companies in Europe and the US. Quotations and proposals are expected to come in starting in 2018, and the final decision will only be made in 2020, reports Reuters.

In a statement made by Niinisto to Finnish reporters, he clarified that there is a purchase set to happen. "It seems that on the sale side, past decisions and hopes about future decisions have mixed," he said, "The purchase is just starting, and that is very clear here."

Possible candidates for the replacement of Finland's F/A-18 Hornet jets include the Eurofighter¬, which is made by Britain, Germany, Italy and Spain, Boeing's Super Hornet, Lockheed Martin's F-35, Saab's Jas Gripen, and Dassault Aviation's Rafale, according to the report.

The F/A-18 Hornet was initially developed by McDonnell Douglas and Northrop in the early 1980s and it was further developed into what is now sold by Boeing as the F/A-18 Super Hornet. According to Boeing's website, they have mentioned only the US and Australia as customers in their F/A-18 Super Hornet page.