PRESSURE on the DUP to end its boycott of the Stormont institutions is expected to intensify ahead of President Joe Biden's visit next month.

Sir Jeffrey Donaldson's party is facing further calls to restore power-sharing in time the 25th anniversary of the Good Friday Agreement.

Tánaiste Micheál Martin and Sinn Féin vice-president Michelle O'Neill joined the chorus of calls over recent days urging the restoration of the assembly and executive on foot of last month's EU-UK deal on the Northern Ireland Protocol.

Their remarks came after Sir Jeffrey suggested the US Senate's majority leader "read some history books" for urging the DUP to get back into government.

Chuck Schumer, who made the appeal at a dinner in Washington DC, said he hoped the Windsor Framework would enable the restoration of power-sharing.

But his words of encouragement were met with a rebuttal from Sir Jeffrey, who responded: "I would urge the senator to read some history books – maybe he'd learn a little bit more about what really happens and the reality of the situation."

The DUP leader has been telling US audiences that while the Windsor Framework represents progress, his party still has reservations.

Speaking on Thursday at the at Ireland-US Council in New York, Mr Martin said the framework "comprehensively addresses the concerns of people and business in Northern Ireland".

"I am hopeful that political leaders in Northern Ireland will embrace this framework and turn their attention to getting all of the institutions of the Good Friday Agreement up and running again, including vital north-south cooperation," he said.

Ms O'Neill said there was an onus on the British and Irish governments, and Stormont parties, including the DUP, to "get back to business and form a government".

"Nine months ago, the people voted in an democratic assembly election, yet no power-sharing coalition government has yet been formed," she said.

"The democratic outcome of that election must be respected."

MPs will next week get their first chance to vote on EU-UK deal when they will be asked to approve regulations to implement the so-called Stormont brake, a mechanism designed to enable the assembly to raise concerns about new EU laws.

Downing Street said the measure, which it is feared could hand a veto to a minority of MLAs, was the "most significant part" of the agreement.

On Thursday, former British prime minister Tony Blair described the deal as the most "practical way forward" to deal with difficulties caused by Brexit in Northern Ireland. He told a Westminster committee the framework was the best that could be done to solve a problem with no real answer.

Meanwhile, Hillary Clinton has said she is hopeful the Stormont institutions will be restored in time for the Good Friday Agreement anniversary.

The former US secretary of state said politicians should either form a government or "resign and let someone from their party who is willing to be part of a new government move forward".