DUP leader Sir Jeffrey Donaldson has said he will make his position on his Stormont seat clear before the end of the week.
Sir Jeffrey has pressed the Government for "decisive action" over the Northern Ireland Protocol before he will nominate ministers for a new Stormont Executive.
He said that "words in themselves will not fix this problem" after the Government stopped short of pledging to take action on the protocol in the Queen's Speech.
Read more: Situation surrounding NI protocol "now very serious", says PM
Sir Jeffrey told reporters in London that he is committed to leading the DUP into political institutions at Stormont.
But he added: "I'm also very clear we need to resolve the issues here in terms of the protocol and I will be making my position clear on that before the end of this week."
Asked if he would stay on as an MP or take up his mandate to be an MLA, Sir Jeffrey said: "In the short term a choice has to be made on that. I will come to a decision with my colleagues."
Following the historic election result at the weekend, Sinn Fein is now the largest party at Stormont and entitled to nominate the first nationalist or republican First Minister.
However the DUP must nominate a deputy First Minister to serve alongside in the joint office.
Sinn Fein's Stormont leader, Michelle O'Neill, said she pressed Prime Minister Boris Johnson on the importance of a new Executive being formed.
She tweeted that she told him the DUP's "refusal to form an Executive is punishing the public, leaving workers and families high and dry".
"The public here can't be a pawn in the British Government's game of chicken with the EU," she said.
"Time to form an Executive now."
Sir Jeffrey said that, during his call with the Prime Minister, he "reiterated our position that we cannot nominate to an Executive until decisive action is taken on the protocol".
Read more: NI's political leaders speak to PM Boris Johnson amid Stormont stalemate
Read more: Stormont latest: What is the Northern Ireland protocol?
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