(AFP) - South Sudan's government declared Friday it has "had enough" of opposition leader Riek Machar, dealing a blow to the latest effort to end more than four years of bloody civil war.

Hopes of a breakthrough rose this week after Ethiopia brokered the first face-to-face meeting in nearly two years between Machar and his arch-rival President Salva Kiir. Regional heads of state also flew to Addis Ababa to apply pressure.

But in a South Sudan government press conference on Friday, the day after the summit, spokesman Michael Makuei condemned the rebel chief in bitter but familiar terms.

"We have had enough of Riek Machar," he said. "As the people of South Sudan, not the president alone, but as the people of South Sudan, we are saying enough is enough."

Makuei rejected Machar's presence in any transitional government, but did not rule out the involvement of other rebel figures.

Machar's SPLM-IO group condemned Makuei's "irresponsible statements" saying they were "intended to derail the peace process."

South Sudan's statement shows the personal enmity between Kiir and Machar, that lies at the heart of the four-year-old conflict, is as strong as ever, despite the handshakes and smiles of recent days.

The world's youngest country descended into civil war in 2013 after Kiir accused Machar, his former deputy, of plotting a coup against him, sparking violence between the two factions that was fuelled by brooding ethnic tensions.

A 2015 peace deal brough Machar back to the capital Juba but it collapsed in July 2016 with fierce fighting that forced him out of the city and into exile in South Africa, where he'd been until the Wednesday meeting with Kiir brokered by Ethiopia's prime minister.

Also speaking at the press conference, South Sudan's acting foreign minister, Martin Elia Lomoro, said fundamental areas of disagreement had yet to be resolved, such as the integration of their two armies, and the allocation of government offices.

- 'Relocate Machar' -

South Sudanese officials declined to say what was discussed in the late-evening rendezvous between Kiir and his bitter foe in Addis Ababa.

But Makuei downplayed the encounter, describing Machar as a serial coup plotter of dubious popularity who Kiir was only meeting casually.

"Politically, we don't want Riek Machar, but he's a South Sudanese. Socially, we interact with him," Makuei said.

"If he wants to be the president he should await elections," he added.

Machar's SPLM-IO rebel group had also taken a hard position at the start of the Thursday summit organised by regional bloc, the Intergovernmental Authority on Development (IGAD), dismissing the peace efforts as "unrealistic".

Lomoro claimed IGAD leaders had agreed Machar could stay in the region for talks before being, "relocated... out of the region, out of any country near South Sudan and [to] anywhere he wants to live."

A landlocked state with a large ethnic mix, South Sudan gained independence from Sudan in 2011 after a long and brutal war.

But initial optimism quickly dissipated and then evaporated altogether at the outbreak of the war, which has killed tens of thousands of people and driven nearly a third of the 12 million population from their homes, with many at the brink of starvation.

Despite the combative rhetoric on both sides, Makuei said his government did not object to Machar attending another round of talks organised by East African leaders for Monday in Sudan, where Kiir and the rebel chief are expected once again to meet.

Similarly, the SPLM-IO said in a statement it remained "confident in the peace process."

© Agence France-Presse