Ukraine crisis: US diplomat casts doubt on Minsk summit
US President Barack Obama has said the option of giving Ukrainian troops lethal aid is still on the table.
His comments came ahead of a meeting in Belarus capital of Minsk - where the leaders of Germany, France, Ukraine and Russia discussed the situation.
"There is uncertainty whether that meeting will take place, and there is great uncertainty whether or not that meeting can actually put together the construct that's necessary," veteran diplomat Thomas Pickering told the BBC's David Willis.
Mr Pickering is the former US ambassador to Russia and the UN.
10 Feb 2015