"Peace all over the world would be the best deal," Trump told the Portland Press Herald, which he gave during his visit to the city.
"And I think I would know how to do it better than anybody else, but peace all over the world," Trump said.
He was responding to a question as to what would be the best deal he could negotiate as president of the US.
Trump, 70, is facing a tough battle against his Democratic rival Hillary Clinton in the presidential elections.
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"Well younger than Ronald Reagan, younger than some, basically I guess Hillary is about that same age, a number of them are about that age. That seems to be a good political age for the presidency if you look it's all around that middle vicinity. I think Ronald Reagan was one of our great presidents and that was an older age, so that's the way we have it," he said.
Later addressing an election rally in Portland, which was marred by a number of protests, Trump spoke about illegal immigrants and terrorism.
"They're all talking about it. Maine, Somali refugees. You admit hundreds of thousands into Maine and into other places in the US. Hundreds of thousands of refugees. And they're coming from among the most dangerous territories and countries anywhere in the world. This is a practice that has to stop," he said.
"People are pouring into our country, we have no idea who they are. This could be the great Trojan Horse of our time," Trump said.
"It's sort of rude, when you think about it. We want jobs, we want health care. We're looking for the same thing. You want to have a good life. You want safety. And then we have people interrupting constantly," he said.