LUXEMBOURG (Reuters) - The European Union urged Russia on Monday to halt its aerial bombing campaign in Syria but the bloc’s 28 member states failed to agree among themselves on whether President Bashar al-Assad should have any role in ending the crisis.

Seeking a common front in their criticism of Russia’s dramatic military intervention in Syria, EU foreign ministers warned that air strikes designed to support Assad could also deepen the 4-1/2-year civil war that has killed 250,000 people.

Ministers also sought to further pressure Assad by agreeing to broaden the EU’s economic sanctions criteria to people benefiting from his government, a move essentially aimed at freezing the assets of the spouses of senior figures, although no names have been added to the EU’s list.

“The recent Russian military attacks ... are of deep concern and must cease immediately,” ministers said in their most strongly-worded statement on Russia’s intervention.

“The military escalation risks prolonging the conflict, undermining a political process, aggravating the humanitarian situation and increasing radicalization,” said the ministers, meeting in Luxembourg.

EU leaders are also expected to criticize Russia at a summit in Brussels on Thursday, EU officials say.

After years of inaction in Syria, the EU is now desperate to stem the flow of migrants into Europe. Its stark criticism of Moscow underscores just how far diplomatic efforts have faltered since a U.N. meeting in New York in late September, when Europe and the United States looked to Russia for help.

Russian incursions into Turkish airspace and air strikes directed not at Islamic State militants but at relatively moderate opposition groups have alienated the West, while leaving EU and U.N diplomacy in disarray, diplomats said.

Plans have evaporated for a ‘contact group’ working with Russia, the United States, Iran and Saudi Arabia to find a post-conflict settlement, while EU diplomats have few ideas about how to find a political solution.

“All Assad’s main opponents are dead, in jail or in exile. And nobody wants another Libya,” said one EU diplomat involved in the discussions, referring to Libya’s collapse after its veteran leader Muammar Gaddafi was ousted.

The EU’s own position on Assad remains unclear, with no agreement on whether he could play a role in agreeing a ceasefire and paving the way for elections, or whether the president should go into exile or immediately to prison.

The EU’s foreign policy chief Federica Mogherini suggested that contact with Assad should be made through the United Nations, but Spain’s foreign minister reiterated Madrid’s view that the West will need to negotiate with Assad to stabilize Syria.

“Negotiations are done between enemies,” Jose Manuel Garcia-Margallo told reporters.

France, which is investigating Assad for war crimes, insisted that the Syrian leader could only be involved in the transition in a symbolic way, and that it must be clear at the start of any negotiation that he would not be there at the end.

“For peace in Syria, we need a political transition. That must be done without Assad,” said France’s European affairs minister Harlem Desir.

Britain says Assad cannot be allowed to remain as president but is willing to discuss how and when he might leave.