The DUP leader was addressing a rally in Bangor, Co Down, where he said both the UK Government and the EU now recognised that the protocol needed to be changed.
Speaking ahead of the rally, Sir Jeffrey said: “Unionism stands united in opposition to the protocol. That must continue to be our focus.
“There are too many divisions. This election will be won and lost on transfers.
“I want every unionist to give the DUP their first preference but I want them to then continue and transfer to the other pro-union candidates.”
The rally is the latest in a series which have been taking place across Northern Ireland outlining unionist and loyalist opposition to the post-Brexit protocol, which sees additional checks on goods arriving into Northern Ireland from Great Britain.
It is strongly opposed by unionists as a border in the Irish Sea.
Earlier this year, the DUP pulled out of the Stormont Executive in protest at the protocol and the party has vowed not to re-enter government after Thursday’s election until their concerns have been addressed.
If Sinn Fein wins this election, the message to London, Dublin and Brussels will be business as usual with the Protocol
Sir Jeffrey Donaldson
Sir Jeffrey continued: “The protocol has driven up haulage costs between GB and NI by 27% and placed a border between us and our most important trading partner – Great Britain as well as jeopardising our medicine supply in the middle of a health pandemic.
“We have made progress in convincing many of the merits of our case. From a position of no renegotiation, the EU and the Government now recognise the need for change.
“The Government knows that the Protocol does not enjoy the support of Unionists and Brussels can be in no doubt that the Protocol has cast its long shadow over Northern Ireland’s political arrangements.
“If Sinn Fein wins this election, the message to London, Dublin and Brussels will be business as usual with the protocol.”
The meeting was also addressed by TUV leader Jim Allister as well as Baroness Kate Hoey and former Brexit Party MEP Ben Habib, who are among a group who have launched legal action against the protocol, which is due to be heard at the Supreme Court.
They also spoke at an anti-protocol rally held earlier in the day in Ballymena, Co Antrim.
Mr Allister told the Co Antrim rally that there can be no return of the Stormont powersharing Executive until the protocol is removed.
A number of loyal order bands marched through Ballymena before several hundred people gathered in the town centre to hear speeches.
Mr Allister said: “We must bring the mendacious Prime Minister who put this iniquitous protocol upon us to the point where he has to make a choice.
“And the leverage we have is to make the Prime Minister choose: do you want to save the protocol, or do you want to save Stormont?
“You cannot have both.
“And the reason I say you can’t have both is very simple: the price of Stormont is to implement the protocol and it is a price no unionist can pay or ever should have paid.”
He added: “The core premise of the protocol is that GB is a foreign country and that Northern Ireland, in trading terms, is an integral part of the EU on what is to be the economically integrated island of Ireland.
“The declaration of GB as a ‘third’ or foreign country cuts to the very heart of the Union.
“Little wonder the Court of Appeal admitted the protocol has subjugated Article 6 of the Acts of Union – the very basis of the economic union of the Union.”
Lady Hoey said: “I think people are angry in the pro-union community.
“I think we are angry at the way Northern Ireland has been treated by our own Government, but also particularly by the way the Irish Government and the European Union have colluded together to do what they could to set Northern Ireland apart from the rest of the United Kingdom.
“I think we all know how the protocol has divided Northern Ireland from the rest of the United Kingdom, the principle of consent which was so crucial to the Belfast/Good Friday Agreement, which many of us voted for.
“Now how betrayed we feel that the principle of consent has been overruled by our own government and by a European Union that used Northern Ireland to punish the rest of the United Kingdom.
“The price of Brexit to the people within the European parliament is going to be Northern Ireland. Well, we are not going to let that happen.
“None of us want to go back to dreadful days of violence but we cannot have a situation where our Government is ignoring the majority community in Northern Ireland.”
Referring to Thursday’s Stormont elections, Mr Habib said: “We have to have a unionist majority in Stormont, we have to use that unionist majority to bring Stormont down.
“There can be no Stormont for as long as the protocol exists.
“If we get that unionist majority then it is down to you people to hold those politicians to account, to make sure that they do what they promised which is to not allow the Executive to form and to ensure Stormont is not reformed until the protocol goes.
“You cannot have Stormont and the protocol, the protocol has to go first.”