Army veteran Doug Beattie has pledged progressive policies and a unifying agenda after being deemed elected as the new leader of the Ulster Unionist Party.
He accepted his party may have to "shrink to grow" as some traditional supporters may not be comfortable with his more liberal outlook.
The Upper Bann MLA will succeed the resigning Steve Aiken as the only candidate to put his name forward for the role of UUP leader.
Ulster Unionist chair Danny Kennedy told a Stormont press conference Mr Beattie was deemed elected, subject to ratification on May 27 by the party council.
Mr Beattie, 55, who served as a soldier for 34 years and was awarded the Military Cross for bravery in combat, said he wants to make UUP policies more clearly understood.
He said: "I feel the weight of expectation on my shoulder. We are a historic party, we are the party of (Edward) Carson and (James) Craig, but we are a modernising party and we are a party that wants to reach out.
"And we will do that by reforming our message, by reforming our party structures, by bringing in more females and more young people, making our policies better understood and more crystallised and reaching to everybody to say that this is Northern Ireland, a place that we all want to live in, and let's all work together to be able to live here."
Mr Beattie said he would reach out to more conservative UUP members to assure them they have "nothing to fear" from his leadership.
But he acknowledged some may ultimately choose to leave the party.
He said: "As the Ulster Unionist Party leader I want to grow and sometimes they say you have to shrink in order to grow and if I have to shrink to grow, that is exactly what I will do.
"But we will look for policies that are progressive. We will look for uniting people, we will look for a union of people over the coming months and the coming years. And we will make Northern Ireland work."
Mr Beattie insisted the Ulster Unionists and DUP, which last Friday elected Edwin Poots as its new leader, are "two distinct and very separate parties".
"I've always seen us as being different. But what we've got here now is an opportunity to reach out to all unionists and say there is a party that you can vote for," he said.
"And I'm obviously pitching that they vote for this party here because we will be the party that will be reaching out to them."
The MLA said dealing with the post-Brexit Northern Ireland Protocol would be a priority, and made clear he would support an UK-EU veterinary deal as a way to reduce agri-food checks.
He accused others of "spinning lies" in claiming Stormont could vote to get rid of the Protocol in 2024.
Mr Beattie said MLAs could only vote to get rid of certain parts of the Protocol and that then triggered a two-year process for those elements to be replaced with something else.
