High-ranking military officers from both sides in the Libyan civil war have held UN-sponsored talks in Geneva for the first time in an attempt to build a lasting ceasefire, the UN special envoy for Libya, Ghassan Salamé, has said.

The talks, likely to last all week, represent progress since for days Khalifa Haftar – the general who leads the self-styled Libyan National Army, based in the country’s east – had refused to attend.

The talks had been proposed by world leaders at a summit in Berlin more than a fortnight ago.

Salamé said the two sides in the civil war – the LNA and the UN-recognised Government of National Accord, based in Tripoli – had each sent five senior officers.

Since the Berlin talks, Salamé said both sides had increased the intensity of fighting and repeatedly breached a UN arms embargo first imposed in 2011.

Salamé claimed “the embargo had been violated incessantly”, and once again appealed to the countries involved in providing arms and mercenary soldiers to desist. “More than 20m pieces of weaponry are already in the country and that is enough. The country does not need that equipment,” he said.

Salamé said the goal of the talks was to turn a nominal truce into a lasting and sustainable ceasefire, covering the removal of heavy weaponry. He said he was working to bridge the gaps between the two sides on the terms of a ceasefire first agreed in principle at the behest of Turkey and Russia.

A proposal from the EU to provide ceasefire monitors will be put on the table at some point, but it will be for the Libyan negotiators to decide if they welcomed this help. There are no plans for the EU to enforce the ceasefire, merely to check its observance and report any breaches.

The talks between the two sides were not face to face on the opening day, Salame said.

The UN envoy for Libya, Ghassan Salamé, at a news briefing before UN-brokered military talks in Geneva, Switzerland on Tuesday. Photograph: Denis Balibouse/Reuters

The GNA has been pressing for Haftar’s forces to pull back to the positions they adopted before he began an assault on Tripoli in April. Haftar has taken up positions south of Tripoli, and captured the coastal town of Sirte, but his plans to capture Tripoli within days have stalled.

The LNA airforce is backed by the United Arab Emirates and receives logistical help from Egypt, as well as hundreds of Russian mercenaries. The LNA has political support from the French president, Emmanuel Macron.

Turkey has sent as many as 2,000 Turkmen fighters from Syria to counter the LNA, leading to warnings by the German foreign minister, Heiko Maas, that Libya could collapse into a second Syria.

Salamé also appealed for Haftar’s forces to end their blockade of the Libyan oil industry, saying their actions have meant Libyan oil production has collapsed to 70,000 barrels a day, down from 1.3m barrels a day before the fighting began. He said it would require international action to lift the blockade, but warned that with 90% of Libyan government revenue dependent on oil and gas exports, a lengthy blockade was not sustainable.

Haftar has partly imposed the blockade to weaken the GNA but also to protest at the way in which the Tripoli-based Central Bank distributes the oil revenues supplied by the Libyan National Oil Corporation.

The success of the ceasefire talks will largely turn on whether the two main external actors on both sides – Turkey and the United Arab Emirates – sense that the political opprobrium of arming their sponsor is outweighing the benefit of developing long-term influence over such an oil-rich state.

Europe, due to internal divisions, has in recent weeks been marginalised from resolving the dispute with Turkey and Russia instead taking a more prominent role.

The UN security council is still working on a resolution demanding the ceasefire is respected, Salamé said, but international divisions are again making agreement difficult.