US President Donald Trump says his predecessor should be blamed for Russia's invasion of Crimea, Reuters reported.

He also reiterated his belief that Russia should be invited back to the elite G7 summit. 

"I would say that the G8 is a more meaningful group than the G7, absolutely," Trump said. 

"You'll have to ask Obama, because he was the one that let Crimea get away" he said when asked about the annexation. "He allowed Russia to take Crimea. I may have had a much different attitude."