The July 16 US-Russia summit in Helsinki could reset a relationship dogged by decades of dangerous rivalry. A man-to-man meeting with Russia's President Vladimir Putin is the kind of encounter that United States President Donald Trump, confident of America's military and economic clout - Russia's entire GDP is less than California's - and his own deal-making ability, seems to relish.

A new strategy for the US, Russia and Iran in the civil war in Syria could emerge from the summit. Mr Trump has indicated he wants to end US involvement in foreign wars. There could be agreement on nuclear non-proliferation, or even on US-Russia mutual nuclear cutbacks.