Arlene Foster said returning a majority of unionist MPs would take the idea of a "divisive and destabilising border poll off the agenda for generations".
Sinn FÃ©in wants to bring a referendum on Irish unity within five years.
Mrs Foster said her party would not have any red lines in upcoming negotiations to restore power-sharing.
But she did set out five core "tests" to be levelled against any agreement:
In a speech launching the manifesto, Mrs Foster said the general election "will go go a long way towards determining whether devolution is restored, or if we are to be ruled directly from Westminster for the next five years".
Saying Northern Ireland needed one strong voice at Westminster, she urged unionists to "unite behind the strongest unionist voice available".
"Gerry Adams has declared that this election will be a barometer on Irish unity," she added.
"Let us rise to that challenge and seek to ensure that unionism still returns a majority of unionist MPs to Westminster and puts the notion of a divisive and destabilising border poll off the agenda for generations to come."
Mrs Foster refused to say if she would stand aside as a nominee for first minister - as demanded by Sinn FÃ©in - until an inquiry over the renewable heating scandal has reported.
But she repeatedly said the issue of who leads the DUP was one for her party alone.
She told party members and journalists: "I took the team into the last assembly election.
"We won that election, therefore we have the right to choose who will be the first minister.
"We don't tell Sinn FÃ©in who they should nominate for deputy first minister."
The manifesto also says the party will:
The leader of the DUP has said maintaining the union with the UK is "by far" the most important issue in the general election.