The White House joined Kiev tonight in accusing Russia of a "flagrant violation of international law" after a convoy of lorries carrying humanitarian aid crossed the border with Ukraine without permission.
It said Russia should remove them immediately, or face further economic sanctions.
ITV News' Europe Editor James Mates reports from Washington:
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Rain will spread eastwards across southern areas tonight. Clear and frosty in the north.
Political leaders will go head-to-head at ITV's studios in MediaCityUK in Salford, ITV has confirmed, as the set for the event is unveiled.
More than 100 people claiming to represent working people across Britain have signed a letter backing Labour in the general election.