France has blunted an EU call for Libyan warlord Khalifa Haftar to halt his attack on Tripoli, despite Nato concern on Haftar's strategic threat.

EU states had aimed to call "on all parties to immediately cease all military operations" and for Haftar to "withdraw" his forces.

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They had also aimed to say his offensive was "endangering civilians, including migrants and refugees ... with the risk of serious consequences for Libya and the wider region, including the terrorist threat".

But that statement was downgraded on Thursday (11 April) to a declaration by EU foreign relations chief Federica Mogherini alone after France objected, the Reuters news agency said, citing diplomatic sources.

The EU is concerned that a civil war in Libya between Haftar and the EU and UN-backed government in Tripoli could prompt more of the 660,000 migrants living in Libya to flee to Europe.

The fighting in the suburbs of Tripoli has killed at least 56 people and displaced 8,000 in recent days, the UN said.

Years of instability have also helped radical Islamist groups and arms and oil smugglers to set up shop in the EU's southern neighbour.

France has built links with Haftar in order to protect its oil interests in the country, but Italy, the EU's other main player in the conflict, has backed the Government of National Accord (GNA) led by Fayez al-Serraj.

"We need more unity, we need to speak with only one voice as Europeans, but unfortunately Europeans are divided on this," the Italian president of the European Parliament, Antonio Tajani, said on Wednesday.

The EU divergence comes amid Nato concern on Haftar's Russian links.

Russia has given money, equipment, training, and diplomatic support to Haftar over the past three years, making it likely that it will want something in return.

"It is public knowledge that General Haftar is strongly dependent on Russia," Yehor Bozhok, Ukraine's deputy foreign minister and former intelligence chief, told EUobserver in Brussels on Thursday.

Russia's sponsorship of Haftar is part of a strategy to create a military "ring around the European Union", ranging from the Baltic Sea region, to the Black Sea, and the furthest regions of the Mediterranean, he said.

Russia already has a military base in Syria.

And a new Russian base in Libya was "difficult to exclude" as a future possibility, Vadym Prystaiko, Ukraine's ambassador to Nato, told this website also on Thursday.

Nato has deployed forces in the Baltic Sea and Black Sea regions to deter Russian aggression, but Russia's Mediterranean posture has prompted a new discussion on the south, Prystaiko added.

"There's a competition about which direction the alliance should go in," he said.

"There are some countries on Nato's southern flank - Italy, Spain, Portugal - who see that their borders are not as well defended as [Nato's] northern borders," he said.

"A Russian base in Tripoli, Libya? This is something that would make Nato have to stretch its forces to the south and the south-east," the ambassador said.

Russia's presence in Syria already gave it control of the flow of refugees to Europe, helping push more than one million people into the EU in 2015 alone and three million more into camps in Turkey.

Philip Mark Breedlove, a former US general at Nato, said at the time it amounted to "weaponisation" of migrants.

And a Russian presence in Libya could make matters worse, Ukraine's Prystaiko said.

"They [Russia] understand that if they push more refugees [to Europe], then Germany, or someone from Germany, will have to call Moscow and try to make a deal," he said.