Syria's President Bashar al-Assad cemented his return to the Arab fold Tuesday when leading Sunni power Saudi Arabia, which long supported Syria's opposition, said its diplomats would resume work in the country.

The restoration of diplomatic ties came more than a decade after Riyadh withdrew its representatives during Syria's civil war, and two days after the Arab League bloc ended Syria's years-long suspension.

Saudi Arabia will host the pan-Arab bloc's next summit on May 19.

The kingdom "has decided to resume the work of its diplomatic mission in Syria," Riyadh's foreign ministry said in a statement carried by the official Saudi Press Agency.

It added Saudi Arabia would seek to "develop joint Arab action".

Assad was politically isolated in the region since Syria's war began, but a flurry of diplomatic activity has been underway in past weeks as a decision by Saudi Arabia and Iran, a close ally of Damascus, to resume ties shifted regional relations.

Three weeks ago Assad met in Damascus with Saudi Foreign Minister Prince Faisal bin Farhan -- the first such visit since the war broke out in 2011.

At that time, Assad and Prince Faisal discussed steps to "achieve a comprehensive political settlement that... contributes to Syria's return to the Arab fold," the Saudi foreign ministry said.

Saudi Arabia severed ties with Assad's government in 2012 and Riyadh had long openly championed Assad's ouster, backing Syrian rebels in earlier stages of the war.

Assad hopes normalisation with wealthy Gulf states can bring economic relief and money for reconstruction, as broader international funding remains elusive without a United Nations-backed political settlement to the conflict.

No political solution

On Sunday the Arab League welcomed back Syria's government.

The body had in November 2011 suspended Damascus over its crackdown on peaceful protests, which had begun earlier that year and spiralled into a war that drew in foreign powers, has killed more than 500,000 people, displaced millions and battered the country's infrastructure and industry.

While the front lines have mostly quietened, large parts of the country's north remain outside government control, and no political solution has yet been reached to the conflict.

Arab League foreign ministers on Sunday emphasised their "keenness to launch a leading Arab role in efforts to resolve" the Syria crisis.

Ahmed Aboul Gheit, head of the 22-member Arab League, said the decision "brings the Arab side into communication with the Syrian government for the first time in years".

Syria's return to the bloc is "the beginning... not the end of the issue", he added, noting it was up to individual countries to decide whether to resume ties with Damascus.

The Syrian National Coalition, the main opposition alliance, said Sunday's decision meant "abandoning" Syrians and leaving them "without official Arab support".

On Tuesday the United States and Britain said they still believed it should not be business as usual with Assad, although they said they would work with Arab states that are reconciling with Damascus.

The United States maintains hundreds of soldiers in Syria as part of a coalition against the Islamic State group. Turkish and Iranian-linked forces are also in the country.