Mary Lou McDonald has called for the restoration of power-sharing at Stormont, saying: "We need government and we need it now".
The Sinn Féin leader was speaking at a press conference at Stormont following the unveiling of the Windsor Framework aimed at ending the deadlock over the Northern Ireland protocol.
The DUP have been boycotting Stormont over the protocol.
Mary Lou McDonald said: "We warmly welcome the fact that the negotiations between the British government and the European Commission have now concluded and that there is a deal on the table.
"We've been meeting today with our team of MLAs because our preparations are now active for a return of the assembly and a return of the executive."
"We believe time is of the essence, we know that we face very very big challenges, economically, socially, in terms of public service provision. We also know there's big opportunities as well for the north of Ireland and the opportunities are coming at us now."
"We're satisfied that the agreement struck does essential things. It ensures there will be no hardening of the border on our island."
"It think a great tribute should be paid to the people and to the electorate who have been incredibly patient and I think at times incredibly frustrated with the entire political process. We need government and we need it now."
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"The team is here and every single one of us is aware we have a big job to do. We're very very anxious to get back to work, none more so than Michelle O'Neill and we await and look forward to the time when she will lead the executive as a first minister."
Ms McDonald added: "All eyes will be on the north of Ireland, and the question it seems to us, for people in politics is, what do you want the world to see?
"Do you want them to see a vista of opportunity and positivity or not. We want these opportunities for every community and all of our people and we hope that our colleagues from other parties are in that same state of mind."
"Perhaps the biggest reform that we need now in this moment is a bit of reformed thinking among some.
"The idea for example that endlessly you can meander along in a state of limbo is not politically real. The world doesn't work like that.
"If I had a magic wand, which sadly I don't have, but if I did and could wish for one thing, I would wish for that level of realism to dawn.
"Because you have whole generations of people who are relying on people like us, elected people in this room and beyond, to actually do the right things, make the right moves and seize all of those opportunities."
Sitting alongside Ms McDonald, deputy leader Michelle O'Neill described the economic potential of this moment as "enormous" and an "opportunity not to be missed".
She added: "Now we find ourselves on the other end of this negotiation, there is enormous potential for us now, a potential that must be grasped.
"I rarely find myself agreeing with the British Prime Minister, but I do think that the opportunity we now have of access to both markets has to be grabbed on to with both hands, and there is no time to waste because we're about to attend in Washington DC a number of events that will be to celebrate St Patrick's Day, but as you all know, that's about encouraging investment here, that's about the economic potential of here.
"We have in quick succession a deal being done on the protocol, we go to the States next week to celebrate St Patrick's Day, very quickly in the aftermath of that comes the anniversary of the Good Friday Agreement.
"The economic potential for us here is enormous and this is a moment not to be missed."
Ms O'Neill said that over the last 24 hours she has been speaking with people, including the business community, and says they have given the deal a cautious welcome so far, and want to examine the detail.
"But that should not delay the formation of an executive, that's where we all should be today, that's where we're focused on and that's the message we believe the public at home want to hear," she said.
"They want to hear when the executive is going to be formed, they want to hear how we're going to tackle together, all of the parties, the huge financial situation that we have ahead of us.
"All the executive parties need to be working together in this time to secure maximum advantage for the people we represent collectively here, and there should be no more delays in all of that."
Earlier today, senior DUP MP Sammy Wilson suggested the Windsor Framework was "not a great deal", as the party leadership takes time to consider its formal position on the agreement.
Declining to say whether it would take days or weeks, he told Times Radio: "As long as it takes us to, first of all, look at the substance of the deal rather than the spin which the government has given."
He lashed out at the Stormont brake, the mechanism by which the assembly can reject changes to EU goods rules.
"The Stormont brake is not really a brake at all. It's a delaying mechanism."
Mr Wilson, the unionist party's chief whip, told Times Radio: "The Stormont brake is not really a brake at all. It's a delaying mechanism."
He said the British government would have the final say over whether to veto a law, which it would be reluctant to do due to being "fearful of the consequences of trade for the rest of the United Kingdom".
