Sinn Fein’s Gerry Adams has warned that the Northern Ireland Secretary is not an acceptable chairman of talks aimed at restoring powersharing at Stormont.
Mr Adams said the republican party is ready to do business with the DUP and the other main political parties in a bid to salvage devolution.
But he warned against James Brokenshire being brought in as a mediator to the negotiations, saying he represents the “partisan” British Government.
“We are here to do business. We are meeting with the two governments and all the parties this afternoon.
“Our resolve is to see these institutions put in place on the basis they were founded upon as quickly as possible. That could be done this time tomorrow morning or dinner time today. They are all rights issues subject to previous agreements.”
Speaking in the Great Hall at Stormont ahead of an afternoon of talks, he added: “We made clear at the beginning of these talks that James Brokenshire is not an acceptable chair.”
Earlier Mr Brokenshire appeared to rule out an independent mediator to chair the Stormont talks amid criticism his impartiality has been compromised by the anticipated Democratic Unionist/Conservative parliamentary deal.
He said the current process - which involves the UK and Irish governments chairing elements of the negotiations and the head of the Northern Ireland Civil Service moderating other discussions - is the “right approach”.
His comments came as DUP leader Arlene Foster warned Stormont rivals participating in the faltering negotiations that the “time for unreasonable behaviour and unrealistic demands is over”.
The talks were paused over the General Election campaign.
With Northern Ireland having been without a powersharing executive since March and without a first and deputy first minister since January, a new three-week process to salvage devolution has begun in Belfast.
However, a major question mark hangs over the talks as a result of developments at Westminster.
Political rivals of the DUP are adamant the UK Government can no longer cast itself as a neutral facilitator in the process, given Theresa May’s intent to form a minority government with the help of a confidence-and-supply deal with the unionist party.
The dispute has prompted renewed calls for a chairman from outside the UK and Ireland to be appointed.
Mr Brokenshire said: “It is important to distinguish what happens at Westminster and the votes that take place here, and devolution and the obligations and responsibilities that we hold fast to in relation to Northern Ireland.”
Devolution in Northern Ireland is based on the template laid out in the 1998 Good Friday Agreement.
The accord commits the UK Government to demonstrate “rigorous impartiality” when dealing with competing political views in the region.
The Secretary of State said the Government remained “four square” behind the Good Friday deal.
A number of deadlines to reach an agreement have already fallen by the wayside since March’s snap Assembly poll, which was triggered by the implosion of the last DUP/Sinn Fein-led administration over a dispute about a botched green energy scheme.
The Assembly election campaign exposed many divisions between the two main parties on issues such as legislative protections for Irish language speakers and how to deal with the legacy of the Troubles.
Mrs Foster said her party remained committed to getting Stormont back up and running.
“I will be engaged with the other local political parties to see if we can achieve agreement to restore our local Assembly and Executive,” she wrote in the Belfast Telegraph.
“To those locally who are complaining the loudest about our position of influence, I say to them that the time for unreasonable behaviour and unrealistic demands is over.”
Irish Taoiseach Enda Kenny called Mrs May on Sunday to warn her the Good Friday settlement has to be protected.
Sinn Fein, the SDLP and Alliance have all made clear they will not accept Mr Brokenshire as a talks facilitator.
He has warned the latest deadline for agreement - June 29 - is “final and immovable”.
He made clear the reintroduction of direct rule from Westminster is on the cards if an agreement does not materialise by that date.
Irish foreign minister Charlie Flanagan said: “It is now more important than ever that we have effective devolved government in Northern Ireland, especially with Brexit negotiations due to begin shortly.
“The Irish Government remains fully committed to ensuring that the Good Friday Agreement and subsequent agreements are upheld and implemented in full.”
The institutions collapsed after the late Martin McGuinness quit as deputy first minister in protest at the DUP’s handling of the ill-fated renewable heat incentive (RHI) - an eco-scheme that left Stormont facing a £490 million overspend.
Powersharing structures meant Mr McGuinness’s move forcibly removed DUP leader Arlene Foster from her job as first minister and triggered March’s snap election.
Leo Varadkar, who is due to be elected the Irish Republic’s prime minister this week, said he would raise the importance of impartiality in powersharing talks when he speaks to Mrs May.
“Our role as guarantors, here in Dublin and London, is to act as co-guarantors and not to be close to any particular party in the north, whether it’s nationalist and republican or unionist,” he said.
“That’s certainly something I’d emphasise in any contacts that I have with Prime Minister May.”
Mr Varadkar also said he sensed the “landscape” around Brexit had changed following the UK election with the influence the DUP can exert and the success of Scottish Conservatives and their desire to avoid a hard split from Europe.