By Lesley Wroughton

PARIS (Reuters) - U.S. Secretary of State John Kerry called on Russia on Thursday to disarm separatists in Ukraine within "the next hours" as the European Union prepared to discuss deeper sanctions against Moscow.

Washington and other Western powers have stepped up pressure on Russia to take concrete action to defuse the conflict in eastern Ukraine, where a ceasefire between Russian-speaking rebels and government forces has appeared to be crumbling.

"We are in full agreement that it is critical for Russia to show in the next hours, literally, that they're moving to help disarm the separatists, to encourage them to disarm, to call on them to lay down their weapons and to begin to become part of a legitimate process," Kerry told reporters in Paris.

He added that EU leaders would discuss possible sanctions on Russia at their summit in Belgium on Friday.

Washington has said it also has new sanctions ready to go, but Kerry said the United States would prefer not to be in "sanctions mode" and wanted Russia to take action without pressure.

"We would like to see a cooperative effort between the United States, Europe and Russia and the Ukrainians," Kerry added.

Separatist rebellions erupted in eastern Ukraine in early April after street protests in Kiev toppled Moscow-backed leader Viktor Yanukovich, and Russia in turn annexed the Crimean peninsula. Eastern rebels have called for union with Russia. Moscow denies Western accusations that it has allowed fighters to cross into Ukraine along with heavy weapons to confront Ukrainian government forces.

The proposed next round of U.S. and EU sanctions would target Russia's financial, defense and high-tech industries, said U.S. officials.

MIDDLE EAST CONFLICTS

Kerry is on a tour of capitals in the Middle East and Europe to discuss Ukraine, as well as the threat to stability in the Middle East from conflicts in Iraq and Syria.

He will meet foreign ministers from the UAE, Jordan and Saudi Arabia in Paris on Thursday. Earlier he met Lebanon's former Prime Minister Saad al-Hariri and Israeli Foreign Minister Avigdor Lieberman.

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The rapid advance of Sunni militants across Iraq threatens to split the country and bring more turmoil into a region already hit by the civil war in Syria.

Kerry travels to Saudi Arabia on Friday for talks with King Abdullah in Jeddah. The United States and Saudi Arabia have both been alarmed by the success of the Islamic State in Iraq and the Levant, or ISIL, in Iraq.

U.S. officials have said Kerry will also discuss the possibility of disruptions to global oil supplies from the Iraq crisis during his meetings in Paris and Jeddah.

Brent crude held steady near $114 a barrel on Thursday as traders watched for possible oil supply disruptions. Iraq's southern oilfields, which produce most of the nation's 3.3 million barrels a day, remain safe although the conflict has hit the Baiji refinery in the north.

(Editing by Mark John and Nicholas Vinocur)