A growing chorus of senior Republican leaders have joined the "anyone but Trump movement," including 2012 Republican presidential nominee Mitt Romney and the last two Republican presidents, George W. Bush and George H.W. Bush.
"Does it have to be unified?" Trump asked about the Republican Party.
"I'm very different than everybody else, perhaps, that's ever run for office. I actually don't think so," he told ABC's "This Week" in excerpts provided ahead today's broadcast.
A group of conservatives opposed to Trump's candidacy meanwhile announced it had launched a "formal effort" for an alternative candidate, though it stopped short of backing a contender from a third party.
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"This is not just a fight for the heart and soul of the Republican Party; it is a battle for the future of our country," Conservatives Against Trump said in a statement.
The race is still "wide open for a qualified conservative candidate," the group of activists said.
"We will not vote for Donald Trump or Hillary Clinton; but we will vote."
Trump, however, said he expected even some Democratic voters to throw their support behind him to win the general election.
"I'm going to go out and I'm going to get millions of people from the Democrats," Trump said.
"But we need absolutely crystal clear and clean water. We
"We don't even know what happens to it...We will create jobs and opportunities for African-Americans and Hispanic Americans that have been failed so badly.
"They've been lied to, they've been cheated to by the Democratic Party. They want their vote, give us your vote, thanks a lot, see you in four years. That's what happens," he said.
Trump said he will stop illegal immigration, deport all criminal aliens and dismantle every last criminal gang and cartel threatening the cities.
They're gonna be out of here. We will also repeal the Obama-Clinton defence sequester and rebuild our badly depleted military," he said.
"We're also going to support our friends in Cuba in their fight against oppression, the oppression of the Castro regime. Tremendous repression. We will demand political and religious freedom for the people of Cuba and stand with our friends in Venezuela in their struggle likewise for freedom we will stand," he said.
The United States, he said, has to stand strong with the state of Israel in their fight against Islamic terrorism.
"And believe me, the Iran deal where we made them rich, we also gave them a direct path right to nuclear weapons. But we'll be working with Israel very closely, very, very closely," he said.