Defence ministers from around the world will gather at the US airbase in Ramstein in Germany on Friday to make it clear to President Vladimir Putin that they stand by Ukraine, British Defense Secretary Ben Wallace says.

"President Putin is banking on us getting bored this year. He’s wrong. We will plan for this year and next year and the year after," he said.

"We’re in it for the long haul," he added.

"It is now time to turn the momentum that Ukrainians have achieved and to make sure Russia “understands that the purpose now is to push them back out of Ukraine” and to restore Ukraine’s sovereignty," he says.