Naomi Long has said she is aiming for Alliance to break through the 20% vote barrier and double the number of Assembly seats it holds.
In an interview with the Belfast Telegraph ahead of Alliance's annual conference this weekend, Mrs Long said the party, which won eight seats in the last Assembly election, could secure between 14 and 18 in the next poll.
She said she wanted to lay the foundations for Alliance becoming Northern Ireland's largest party.
In a wide-ranging interview, Mrs Long revealed that relations between the DUP and Sinn Fein in the new Executive are "more strained" than before because of three years without devolution.
But she said there was more "open debate" and a healthier atmosphere around the table than previously.
The Alliance leader said that next week's Renewable Heat Incentive inquiry report shouldn't be used as an opportunity for the parties to "tear strips off each other and make things more difficult".
Rather than a "highly personalised" response targeting individuals, the focus should be on reforming the system to ensure that past mistakes are never repeated.
Amidst speculation about explosive exchanges with Arlene Foster during the talks to restore devolution, Mrs Long said it was totally untrue to suggest she disliked the DUP leader.
I have no trouble looking at the 20% vote threshold and saying, that's our next challenge. You have to aim high. There is no ceiling on my ambition for Alliance
"On a personal level, I like Arlene and get on well with her," she said. "We probably clash because we're both direct and straight talking so if we disagree on something we go head-to-head, not around each other's backs.
"I prefer that approach to politics. I welcome getting to know Arlene better as First Minister around the Executive table. There is no personal animosity at all."
Mrs Long said her party had started 2019 hoping to break through the 10% vote barrier.
She was "shocked" at how quickly it had grown, securing 17% in the Westminster poll and 18.5% in the EU election, where it "didn't scrape the third seat but took the second".
Stephen Farry's election as North Down MP "laid waste to the old lie that winning East Belfast in 2010 was a fluke and we would never do it anywhere else".
Mrs Long said: "I have no trouble looking at the 20% vote threshold and saying, that's our next challenge. You have to aim high. There is no ceiling on my ambition for Alliance.
"I would love us to become the largest party in Northern Ireland. I don't know that it will happen on my watch but I want to build the foundations."
Mrs Long said her party's membership had doubled in two years. She believed it could now win Assembly seats in West Tyrone, Upper Bann, East Londonderry and North Antrim next time and take two in some other constituencies so it would be "challenging for between 14 and 18 seats" and added that she had "no regrets" about entering the Executive rather than going into opposition.
"You can't ask people to make compromises when you're not willing to do so yourself," she said. "I don't want to be outside the room criticising what's going on, I want to be inside trying to shape it."
The biggest challenge is to avoid this (RHI) becoming highly personalised and about individuals. It's about addressing the systemic failures and ensuring that those things done wrong in the past won't happen again
She said it wasn't "an easy executive, it's difficult". The parties would "cross swords at times" but there had been "no fireworks". There was an "open, healthy" debate at the table.
"There are some bumps in the road ahead," she said.
"The budget will be difficult, the RHI report won't be easy. But it should not be used as an opportunity to tear strips off each other and make things more difficult.
"The biggest challenge is to avoid this (RHI) becoming highly personalised and about individuals. It's about addressing the systemic failures and ensuring that those things done wrong in the past won't happen again."
She said she didn't know if the report would recommend "police investigations, potential prosecutions for illegality" or whether the conclusion would be that the RHI scheme was just badly managed.
She said progress had already been made on addressing some of the issues raised at the cash-for-ash inquiry - codes of practice and pay for special advisers, ministerial accountability, transparency and record keeping.
On the murder of Paul Quinn, Mrs Long called on Sinn Fein Finance Minister Conor Murphy to "specifically and unambiguously" state that the 21-year-old Cullyhanna man wasn't a criminal.
I wouldn't be as presumptuous as some to say a border poll is inevitable in five or 10 years, but I do think it is more likely than it was previously
"When you're a politician, you have a lot of influence. What you say carries weight in the community. You're an opinion-former. So when you say somebody's a criminal, that has implications for whether people are willing to come forward with information to the police," she said.
"It is important that Conor does say that Paul Quinn wasn't a criminal. The pain that Breege and Stephen have been through is horrendous. Their son's awful death was added to by the fact that he was smeared publicly.
"They live this nightmare every day. I would hope that Conor would find it within himself to bring a measure of peace to this family."
Asked about the possibility of a border poll in her lifetime, Mrs Long said the chances had increased due to Brexit.
"I wouldn't be as presumptuous as some to say a border poll is inevitable in five or 10 years, but I do think it is more likely than it was previously," she said.
The theme of Alliance's conference is '2020 Vision' and the party will be celebrating its 50th anniversary. Mrs Long said she wished to "pay tribute to those who came up with the idea of a cross-community party in 1970, the grimmest of times".