ATHENS -- EU foreign ministers stressed the need Saturday for Russia to defuse tensions with Ukraine following a two-day informal meeting that ended with leaders insisting that all options remain on the table -- including further sanctions.

Swedish Foreign Minister Carl Bildt stressed the need for resolve in dealing with Moscow after it annexed the Crimean Peninsula in March -- arguing that Russia had deviated from accepted norms. Unity among the 28 member states was critical.

"We should be very firm on international law and the rules that must apply," he said.

Bildt took it a step further, underscoring Western unease with the Crimean referendum, which was called just two weeks after Russian forces had overtaken the Ukrainian region. Ukraine and the West have rejected the vote and the annexation.

Bildt, who served as a mediator in the Balkan conflict, said that outsiders must start thinking about Russia's motives in the complex interplay of faith and power.

"We are having a profound debate on what is the nature of Russia ... I think it's pretty clear that Russia has changed in the last few years," he told reporters outside the session in Greece. "There is a new political mentality, at least from the Kremlin. They are intending to build up... an Orthodox bastion against the West."

Referring to a public rally last month in which Russian President Vladimir Putin spoke in front of a banner reading "Crimea is in my heart," Bildt said, "You have to ask yourself, what else is in his heart?"

Speaking just before the meeting got under way Friday, British Foreign Secretary William Hague urged EU partners to develop stricter sanctions for possible use against Russia should they become necessary. The EU has so far imposed sanctions against individuals.

The informal meeting involved just the 28 ministers, without the presence of assistants, to facilitate debate, in a tradition reaching back to 1974. Foreign ministers of EU candidate countries, as well as the chairman of the European Parliament's Foreign Affairs committee, were invited to join on Saturday, the final day of the meeting.