"It isn't certain, it is under stress, it is fragile".
She has already met with the DUP to seek a deal to support a minority Conservative government.
"The last thing anyone wishes to see is one or other of the communities so aggrieved the hardmen who are still lurking in the corners return to some form of violence".
"The Prime Minister and I will meet the five main Northern Ireland political parties in Downing Street tomorrow to build on the political discussions that restarted on Monday in Belfast", he said.
"The intent is to ensure that we have the stability of Government in the national interest".
"There's no room for any side deal with the DUP", she said.
Seeking to avoid a second election that could deepen Britain's worst political turmoil since last June's shock vote to leave the EU, May edged closer to a deal to get support of the Democratic Unionist Party (DUP).
Her failure to win a majority has put May under pressure over her Brexit plans from inside and outside her party and has prompted complaints about her choice of partner due to the DUP's stance on social issues such as gay marriage.
Special counsel Mueller investigating Jared Kushner's finances, Washington Post reports
Less than an hour later, Trump sent out another tweet, this one aimed directly at Rosenstein. The newspaper also said Mueller was looking into money laundering by Trump associates.
She also gave a glimpse into the issues on the table, saying Brexit, counter-terrorism and "doing what's right" for the Northern Ireland economy were among the key issues being thrashed out.
She reportedly apologised to Tory MPs, accepting personal responsibility for failing to win an outright victory and sacrificing the parliamentary majority she inherited from David Cameron when she became leader after the Brexit referendum past year.
The DUP continue to hammer out the details of the deal with the Tories.
He said: "I'm sure we all look forward to welcoming the Queen's Speech just as soon as the coalition of chaos has been negotiated".
A deal may not be reached until Monday, it has been suggested, pushing back the Queen's Speech to present the government's programme until the follow week.
But a deadly fire at a tower block in London delayed the announcement of any deal.
Despite the uncertainty over her ability to govern, May had confirmed that Brexit negotiations - expected to be the most complex worldwide talks Britain has held for decades - would begin as planned next week.
'It's going to be hard, there's no doubt about that, but perhaps an opportunity to consult more widely with the other parties on how best we can achieve it, ' Cameron was reported by the FT as saying at a conference in Poland on Tuesday.
Besides the date, they were also discussing the precise format of the talks, if the four-week cycles proposed by the European Union would be acceptable to the United Kingdom, and technicalities, such as whether to hold joint press points at the end of each negotiating round.