Gerry Adams has dismissed speculation that Sinn Fein had lost interest in Stormont as his newly-elected MPs headed to London.
The Sinn Fein president argued that devolution provided "a strategic route" towards a united Ireland.
On the first day of a two-day visit, the seven republican MPs had a series of meetings, but continued the tradition of staying away from the House of Commons chamber.
There was speculation the group might meet Labour leader Jeremy Corbyn, although there was no confirmation yesterday.
With the MPs in the UK capital, Mr Adams was in Dublin, where he urged incoming Taoiseach Leo Varadkar to get more directly involved in the negotiations aimed at restoring devolution.
Mr Adams also firmly denied that his party's focus had shifted as a result of the Brexit vote.
"The focus has to be on plan A, which is to get the institutions in place, that is our focus and we would like to think it will be the focus of the incoming Taoiseach," he said.
"We want into the institutions, because that is what the people desire, that is what the people voted for.
"But also because we think, strategically, that is the way to a united Ireland.
"The way forward is not to be in a vacuum, to have stagnation, the way forward is to have that forum working on the basis on which it should have been established."
Meanwhile, the smaller parties have complained that the Stormont talks to restore devolution are failing to gain momentum. The first round-table session involving all five parties and the British and Irish Governments is not expected until tomorrow.
That leaves just a fortnight until Secretary of State James Brokenshire's "immovable" deadline of June 29, after which a decision must be taken on the return of direct rule.
Inter-party meetings, mostly involving officials, continued yesterday but the focus of interest had shifted to the talks in London between the Conservatives and the DUP.
Irish Foreign Minister Charlie Flanagan is also expected to be absent today because of events surrounding the incoming Taoiseach in Dublin.
Back in Belfast, SDLP leader Colum Eastwood said there was "deep suspicion and concern that a public deal between Theresa May and Arlene Foster might be accompanied with a private, grubby back room deal which none of us will get sight of for years to come".
"It is in the interests of all our people that we are given full transparency. It is also the only way to address the public's suspicion and concern," he insisted.
Alliance deputy leader Stephen Farry said the lack of an all-party round-table until Thursday at the earliest "doesn't inspire confidence".
Most of the parties have met Mr Flanagan and Mr Brokenshire since Monday, but Mr Farry said: "There remains no impetus. We need people to step up to the plate, and do so without delay.
"The consequences of not doing so are too severe."
Meanwhile, UUP leader Robin Swann said seeking an independent chairperson for the talks was "futile".
Nationalists have complained that Mr Brokenshire cannot be an "honest broker" because his party is seeking a deal with the DUP at Westminster.
Mr Swann said: "We have a few short weeks to restore devolution. Let's not waste any more time dancing around on the head of a pin."