BRUSSELS (Reuters) - The European Union imposed sanctions on three Libyan political leaders on Friday for opposing a U.N.-backed unity government for the country, a move aimed at weakening so-called spoilers of the peace process.

EU states are also considering deploying a civilian security mission in Libya to back the new unity government led by Prime Minister Fayez Seraj, an EU official said.

The asset-freeze and travel ban measures were formally adopted on Thursday to take effect on Friday, two days after the members of the Libya’s unity government reached Tripoli by ship, defying attempts to keep them out of the city.

Fearful of derailing efforts to forge peace between Libya’s two rival governments in Tripoli and Tobruk, EU governments hesitated for months before agreeing in March to move on with restrictive measures.

The three men sanctioned are Nouri Abusahmain, president of Libya’s General National Congress in Tripoli, Khalifa al-Ghwell, prime minister of the self-proclaimed Tripoli government, and Aguila Saleh, the president of Libya’s internationally recognized parliament in Tobruk.

The EU said the three played a central role in obstructing the establishment of a unity government in Libya, which has become the main conduit for refugees from North Africa and sub-Saharan Africa to leave in boats for Europe.

The measures will be regularly reviewed and “can be amended to take into account developments on the ground,” a spokesperson for the EU foreign affairs services said.

A regular EU meeting of national political and security experts on April 5 will focus on “a future possible civilian European security and defense mission in Libya,” an EU official said on Friday.

EU security experts could be sent to Libya to train security forces and improve border controls, the official said, although concrete preparations for the mission would start only after Libyan authorities formally request it.

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Once such a request is received, it could take a few weeks for the EU experts to be deployed, the official added.

In a letter sent to EU foreign ministers in March, the EU foreign policy chief Federica Mogherini urged them to consider “the possibility of setting up a team of ‘deployable experts’ on migration and security issues”.

EU defense and foreign affairs ministers will hold a joint meeting focused on Libya on April 18 in Luxembourg.