The sale of the missiles is likely to anger Russia, which this week unveiled a range of new generation weapons which President Vladimir Putin said would counter the threat from the US.

"This weapon in the hands of the Ukrainian military will become an additional deterrent argument against Russian aggression in Donbas," Poroshenko wrote on Facebook, referring to the eastern region where Kiev has fought a Russian-backed insurgency since 2014.

"I am thankful to President Donald J. Trump and the entire team that supports Ukraine for this important historic decision," he added.

According to the US Defense Security Cooperation Agency, Ukraine asked the Trump administration for permission to buy 210 Javelin missiles and 37 launchers at a cost of around $47 million.

"The Javelin system will help Ukraine build its long-term defense capacity to defend its sovereignty and territorial integrity in order to meet its national defense requirements," the agency said in a statement on Thursday.

US government employees and contractors will help transport the weapons and train Ukraine's forces to use them.

The United States and its Western allies back Ukraine in its struggle to reunite its country after Russia annexed the Crimea region and pro-Russian rebels seized two eastern industrial regions.

But the US has been cautious in the past about escalating the conflict that has left over 10,000 dead by providing advanced "lethal" weaponry to Kiev, which may provoke a further degradation in tense ties with Moscow.