Arlene Foster has suggested her Democratic Unionist Party (DUP) could revisit its confidence and supply agreement with the Conservative Party if Theresa May's Brexit deal passes through parliament.
The Northern Irish party has said it will not be able to support Ms May's deal unless she ditches the proposed backstop, which would see increased regulatory checks between Northern Ireland and the rest of the UK.
Speaking ahead of the DUP's annual conference this weekend, Ms Foster warned that the EU Withdrawal Agreement will not get the support it needs from MPs and instead of "wasting time" on the agreement, she said Mrs May should try to secure a better deal.
"If this is not going to deliver on Brexit then of course that brings us to the situation of looking again at the confidence and supply deal," she told the BBC. "But we are not there yet."
The uncertain future of the confidence and supply agreement, introduced after Ms May lost their parliamentary majority at the 2017 general election, raises fresh questions over the ability of the government to pass crucial legislation.
Under the terms of the deal, the DUP agreed "to support the government on all motions of confidence, and on the Queen's Speech, the Budget, finance bills, money bills, supply and appropriation legislation and Estimates".
Philip Hammond, the Chancellor, met with Ms Foster and her deputy Nigel Dodds in Belfast ahead of the DUP party conference.
Mr Hammond said that the government was considering providing extra border backstop assurances to the DUP to ensure their support.
He said that ministers have a number of choices through the parliamentary process, which includes extending the Brexit implementation period ahead of the permanent relationship.
That could avoid having to use a backstop, in which the UK would continue to follow EU regulations relating to trade across the Irish border - a solution which is adamantly opposed by the DUP.
Earlier in the week the DUP raised questions about the future of the confidence and supply agreement after MPs pulled their support by abstaining on a number of key budget votes.
All eight of the party's MPs present in the Commons abstained on three votes, and even joined forces with Labour to support one amendment relating to child poverty.
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