European Union sanctions will send a "very tough message" to Russia, according to Prime Minister David Cameron.
He said: "The sanctions really relate to Vladimir Putin's and Russia's behaviour, and we want to make it absolutely clear that Russia's behaviour in destabilising another country - Ukraine - is unacceptable."
He added: "It was very clear in my conference call with President Obama, President Hollande, Chancellor Merkel and prime minister Renzi yesterday that we are united in sending that very tough message. It's a message that will be backed by tough action."
The measures will shut state-owned Russian banks out of European capital markets and target the defense sector and sensitive technologies, including oil.
However the the gas sector, on which Europe is heavily dependent, is not expected to be included when the sanctions which are likely to be announced tomorrow.
More top news
Theresa May is considering options to secure statutory powers for child sex abuse inquiry but it may require 'disbanding' current panel.
London mayor Boris Johnson is backing Olympics supremo Seb Coe as his replacement.
A top Fifa official who assessed rival bids to stage the 2018 and 2022 World Cups revealed England’s was by far the strongest contender.