White House adviser Tony Blinken says there is evidence that Russia is preparing to deliver more powerful rocket launchers to separatist rebels in eastern Ukraine.
Western powers have accused pro-Russian rebels in the area of shooting down Malaysia Airlines flight MH17 with a rocket.
More top news
Socialite Tara Palmer-Tomkinson has been cautioned by police after a 'disturbance' at Heathrow Airport.
The NHS is to set up 11 centres to unlock the secrets of DNA and help develop tests and drugs to target cancer and rare genetic diseases.
Australian businessman named as Alan Sugar's newest apprentice and winner of a £250,000 investment in his fledgling company.