"Talks with the DUP are progressing well and there is broad agreement on the principles of the Queen's speech".
Theresa May's Conservatives have reached broad agreement with Democratic Unionists on a program for governing the United Kingdom, buying the prime minister crucial time as she seeks to finalize a longer-term agreement with the Northern Ireland party.
The state opening, a ceremony full of pomp in which the monarch reads out the Queen's Speech detailing the government's programme for the coming year, was due to take place on June 19.
The Conservative source said both parties were "committed to strengthening the union, combating terrorism, delivering Brexit and delivering prosperity across the whole country", and that Northern Ireland would get a funding boost.
The Prime Minister's new Government is dependent on the support of 10 DUP MPs to remain in place because the Tories lost seats at the snap election.
Brexit Secretary David Davis said parts of the Tory manifesto had to be "pruned away" because they would not command support from the Commons.
May is due to host the leaders of all Northern Ireland's parties at Downing Street to talk about the potential implications of any deal with the DUP over power sharing at Stormont.
After days of uncertainty, the Government announced that the State Opening would now take place on Wednesday June 21 - two days later than originally scheduled.
Such a deal involves the minor party agreeing to support the Government in confidence votes, and in "supply" votes to pass financial orders to keep Whitehall and departments running.
Following her meeting with Mrs May, Alliance Party leader Naomi Long said the PM had "sought to give us her reassurance on neutrality".
The 1998 Good Friday Agreement, also referred to as the Belfast Agreement, requires the United Kingdom and Irish Governments to show "rigorous impartiality" as they deal with the different political groups in Northern Ireland.
He said Mrs May must immediately create a cross-party joint cabinet committee to negotiate the UK's exit.