After weeks of intense London-Brussels talks, momentum has been building towards a deal to revise the Northern Ireland Protocol - the arrangements agreed to avoid a hard border with EU member Ireland when Britain exited the EU in 2020.

"I had positive conversations with political parties in Northern Ireland," Prime Minister Rishi Sunak told reporters. "There's work to do, we have not got a deal yet."

One EU diplomat said it appeared the two sides were edging towards agreement and that a meeting in Brussels between British Foreign Secretary James Cleverly and EU Brexit chief Maros Sefcovic could prepare the ground for a rapid conclusion.

"We have been at this sort of stage before so nobody is ready to uncork the champagne yet," another EU diplomat said.

In Belfast, Sunak focused his attention on the Democratic Unionist Party, whose opposition to the protocol must be overcome to make any deal work.

"I will simply say that on some very important issues I think there has been real progress," the DUP's Jeffrey Donaldson, who unlike other political leaders met Sunak late on Thursday as well as on Friday, told reporters afterwards.

"But there remain some outstanding issues that we need to get over the line, and we will then examine the final text of any agreement very carefully."

The DUP have proven to be central players in almost seven years of often tortuous Brexit talks and their resistance has torpedoed previous attempts at agreement. Donaldson said his party would keep working until an outcome meets its red lines.

After Sunak's team spent far longer with his delegation than any of the other parties on Friday, Donaldson added that he did not know when a deal could be reached and that the role of the European Court of Justice (ECJ) was part of the ongoing talks.

The talks have been shrouded in secrecy since a drastic improvement in relations under Sunak, but some of the main players have complained that the prime minister's high-wire strategy has left them without any detail on the possible fixes to issues including the role of the ECJ.

The meetings underlined that support in Belfast and among eurosceptic lawmakers in Sunak's governing Conservative Party will be key to whether London and Brussels can finally put their post-Brexit spat over Northern Ireland behind them.

The response of the DUP, Northern Ireland's largest pro-British party, is particularly crucial due to its year-long boycott of the region's devolved power-sharing parliament in protest at the protocol.

Opinion polls have consistently shown a majority of Northern Irish voters - who earlier opposed Brexit - favour the idea of the protocol, but the imposition of checks on some goods coming from the rest of the United Kingdom has angered many pro-British unionists who see it as undermining the union with Britain.

"HARD WORK" TO CONTINUE

In Brussels, European Commission Vice-President Sefcovic said that hard work would continue after his meeting with Cleverly that both sides described as "constructive".

Sefcovic then briefed EU ambassadors, indicating talks were going in the right direction and that a deal might soon be possible - but without indicating when, EU diplomats said.

"Upbeat, but not there yet," was the assessment of one EU diplomat.

Irish Prime Minister Leo Varadkar said he was quietly confident that they could be in a position to sign off an agreement in the next week or two.

"We are getting there," he was quoted by RTE as saying.

Sunak will meet European Commission President Ursula von der Leyen in Munich on Saturday to address the state of play.

The two sides have already reached agreement on data-sharing and, in a bid to reduce checks at Northern Ireland ports, the European Commission has said it was open to the idea of "express lanes" to separate goods bound only for Northern Ireland from products heading into Ireland or elsewhere in the EU.

Brussels insists the ECJ must be the ultimate arbiter of disputes relating to its single market, of which Northern Ireland remains a part for goods trade, while some members of Sunak's Conservatives and the DUP see continued ECJ jurisdiction over any UK territory as an infringement of British sovereignty.

The other political parties that met Sunak on Friday said detail from the prime minister on a potential deal was "scant".

Sinn Fein, the former political wing of the militant Irish Republican Army that wants Northern Ireland to split from the UK and unite with Ireland, became the province's largest party for the first time at elections last year.