CAMERON: We're willing to take sanctions on Russia 'to a whole different level'

UK Prime Minister David Cameron is taking a harder stance on Russian president Vladimir Putin than his French and German colleagues.

In an interview with the Wall Street Journal published early Friday, Cameron said the UK would be ready to take Russian sanctions "to a whole different level" if there was another surge in violence in east Ukraine, and that western nations should prepare themselves for a long-term struggle against Russia.

Cameron, unlike French President Francois Hollande and German Chancellor Angela Merkel, wasn't in Minsk for the ceasefire talks with Ukrainian President Petro Poroshenko and Putin. Cameron was thought to be closer to the US position, which is more open to helping further arm the Ukrainian government.

Here's the WSJ on Cameron:

On events in Ukraine, he said the West must be prepared "to settle in for a long and determined position" of pitting the weight of the U.S. and the EU against Russia.

"If Russia is going to rip up the rule book of the 21st century and destabilize a sovereign country, then the rest of the world should be prepared to say to Russia, 'Well you can't rip up one part of the international rule book while still having access to international markets, international finance, international systems,'" Mr. Cameron said.

Merkel has also suggested the possibility of tougher sanctions recently. Here's what she said on Wednesday, according to Deutsche Welle:

"There is a link between current sanctions and complete implementation of Minsk so that Ukraine officials will have access to their own frontier," Merkel said in Brussels. "Territorial integrity can only be restored if you have Ukraine officials on the Russian border. That is what we are working on."

So far, the ceasefire arranged by European leaders at Minsky has been spotty at best, with violence continuing in many parts of eastern Ukraine.

Russian opposition politician Boris Nemtsov, who was assassinated last week, was investigating the deaths of Russian troops in eastern Ukraine, according to a Reuters exclusive. Russia officially denies sending troops to fight in eastern Ukraine.