The Tories have dropped changes to the triple lock for pensions and winter fuel payments in order to secure a deal for a with the Northern Irish DUP for a working majority.
Outside Downing Street, the DUP leader, Arlene Foster, said a £1.5bn funding package for Northern Ireland has been secured as part of the deal.
The money will be used to boost the region's economy and invest in new infrastructure, health, education and other sectors, she said.
She added that the funding would "address the unique circumstances" of Northern Ireland and the impact on its people.
UK-wide, the pensions triple lock will also stay in place and there will be no means-testing of winter payments.
The DUP and Conservatives have also agreed that a Nato commitment to spending 2 per cent of GDP on the armed forces will be adhered to, and that the Armed Forces' covenant will be fully implemented in Northern Ireland.
"Our aim in these negotiations has been to deliver for all of the people of Northern Ireland," Ms Foster said.
"And the support measures which we are announcing will be to the benefit of all our people."
The DUP leader said the financial support would be made up of £1bn in new funding over the coming two years, as well as "new flexibility" in almost £500m already committed to the region.
Ms Foster said she would return to Northern Ireland for talks aimed at restoring a powersharing executive in Stormont, which was collapsed by Sinn Fein earlier this year amid a growing rift between the party and the DUP.
Both sides have until the end of the week to do a deal.
"Now, more than ever, our political leaders both locally and nationally need to work together to find solutions for all of the people we serve," added Ms Foster.
The agreement restates the Government's support for the Belfast Agreement and the restoration of devolved government in Northern Ireland.
And it seeks to allay concerns over the Government's neutrality in negotiations, by saying that the DUP will have "no involvement in the UK Government's role in political talks in Northern Ireland".
Under the terms of the agreement, the Government has agreed to guarantee that cash support for Northern Irish farming will continue at the same level until the end of the Parliament in 2022, as the UK goes through Brexit.
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