BELFAST — The Democratic Unionist Party (DUP) will not go back into government in Northern Ireland until its concerns about post-Brexit trading arrangements are resolved, the party's leader has said.

Sir Jeffrey Donaldson was among the party leaders to meet with NI Secretary Brandon Lewis in Belfast on Monday. Thursday's historic election saw Sinn Féin become Stormont's largest party.

Would-be first minister Michelle O'Neill said there could be no attempt by the DUP to "punish the public".

O'Neill and Sinn Féin President Mary Lou McDonald held talks with Lewis, who also met with the leaders of the Alliance Party, Ulster Unionist Party (UUP) and Social Democratic and Labour Party (SDLP).

The Democratic Unionist Party (DUP) is resisting pressure from the UK and Irish governments, as well as Northern Ireland's other main parties, to nominate ministers after the dramatic election result.

For months, the DUP has protested against the Northern Ireland Protocol, part of the UK's Brexit deal with the European Union which retains free trade across the Irish border.

It has angered some unionists for introducing new checks on some goods moving across the Irish Sea. They also say it undermines Northern Ireland's place in the UK.

In his meetings on Monday, Lewis urged the party leaders to respect the outcome of the election on Thursday and re-establish Stormont as soon as possible.

He said the government would have to address issues relating to the protocol and "continue to press the EU to agree the crucial changes that are urgently needed".

The NI Secretary stated that he would remain in close contact with all the party leaders over the coming days.

Sinn Féin, whose ultimate goal is for Northern Ireland to leave the UK and become one country with the Republic of Ireland, won the most seats — 27 out of 90 — after Thursday's vote.

This means the party can nominate Northern Ireland's first minister, an unprecedented move for a nationalist party, but it is reliant on the Democratic Unionist Party (DUP) taking up its position as deputy first minister.

The roles form a joint office, with equal responsibility; however, the allocation of the titles is regarded as symbolically important.

Sir Jeffrey said his party would not nominate ministers until there had been "decisive action" on the protocol.

"They (UK government) gave a firm commitment to protect our place in the UK internal market," Sir Jeffrey said.

"They have not done so, they have failed over the last two-and-a-half years to honor that commitment."

But O'Neill said the DUP and the UK government must respect the election's outcome, and that it was down to Boris Johnson and the EU to resolve differences over the protocol.

"Brinkmanship will not be tolerated where the north of Ireland becomes collateral damage in a game of chicken with the European Commission," she said.

"Make no mistake, we and our business community here will not be held to ransom."

While some assembly members (MLAs) were at Stormont on Monday, the legislative body will hold its first sitting on Friday, when members will register and designate as unionist, nationalist or other. — BBC