Tougher EU sanctions against Russia will be needed if Moscow does not change its "approach" to the downing of the Malaysia Airlines plane over Ukraine, UK Prime Minister David Cameron has indicated.
Cameron said the EU should stand up for its principles, amid claims Russia-backed rebels were involved.
Writing in the (Sunday Times), he said it might be "time to make our power, influence and resources count".
The Russian ambassador to the UK Alexander Yakovenko warned sanctions would have a negative effect, according to the (BBC).
Yakovenko said he regretted recent decisions by the US and EU to impose sanctions, claiming it could only "encourage the Ukrainian authorities to continue violence".
In a related context, UK's new Defence Secretary Michael Fallon warned Russian President to "get out of east Ukraine", accusing Russia of "sponsored terrorism".
He told the (Mail on Sunday) 'We have to make it very clear if there is any more interference like this - and it turns out he was behind it - there will be repercussions. He has to be clear the West will act." Ten Britons were among the 298 people killed when the Boeing 777 was downed on Thursday over eastern Ukraine.