London (AFP) - The EU is ready to toughen sanctions against Russia over the Ukraine plane disaster, British Prime Minister David Cameron said Monday, indicating that it could target whole sectors of the economy including goods with possible military uses.

European Union foreign ministers meet on Tuesday to decide whether to broaden sanctions if President Vladimir Putin does not press Ukraine's pro-Kremlin separatists to allow access to the crash site, and reduce Moscow's support for the rebels.

The 28-member bloc has previously imposed sanctions on some of Putin's allies, but is considering wider measures after Malaysia Airlines flight MH17 crashed on Thursday following what is believed to be a strike by a surface-to-air missile.

"In terms of sanctions, I'm very clear having spoken to (German Chancellor) Angela Merkel and (French President) Francois Hollande that the EU will be ready to take further steps, in terms of other areas... particularly some forms of advanced industrial goods that might have dual uses for defence purposes as well," Cameron told Sky News television.

Cameron criticised some EU states at the weekend for failing to take tough action against Russia, and on Monday he urged the bloc to show a united front in the wake of the crash.

"Change is required and the countries of the EU now need to show real purpose and real solidarity in delivering that message to Russia," he said.

Cameron said he had given Putin a warning when they spoke by telephone on Sunday night for the first time since the crash, in which 10 Britons were among the 298 people killed.

"The world today is watching Russia, the world is watching Putin, and everybody wants to know that he will do everything in his power to make the separatists open up that site so there can be a proper investigation," Cameron said.

So far Brussels has only imposed so-called second tier sanctions such as travel bans and asset freezes on members of Putin's inner circle.

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Deputy Prime Minister Nick Clegg said it was it was time for the EU to move to "Tier 3" sanctions which would block access to European markets for whole sectors of the Russian economy, for example gas and oil.

"We believe the time has now come for sanctions to be tightened further and that is precisely what we will be seeking to deliver in the meetings in the EU later this week," Clegg told a monthly news conference.

Finance minister George Osborne told the BBC that EU countries had to be prepared to take an economic "hit" as a result of imposing sanctions against Russia.

London believes some EU countries are more reluctant to impose sanctions, such as Germany, which relies on Russian energy supplies, and France, which has a contract to supply Russia with two warships.