Trump made the remarks after meeting Japanese Prime Minister Shinzo Abe to discuss the June 12 summit.
"Maybe we'll start with the White House," he told reporters after he was asked whether he would invite the North Korean leader to the White House or Mar-a-lago.
About the personal letter delivered to Trump from Kim last week, he said, "The letter was just a greeting. It was really very nice. Perhaps I can get approval to put it out. It was really a very warm letter, a very nice letter".
"I appreciated it very much, and nothing other than. 'We look forward to seeing you, and we look forward to the summit, and hopefully, some wonderful things will work out'. So it was really very warm, very nice. We appreciated it," Trump said.
He, however, made it clear that he was ready to "walk away" from the meeting if his goals were not achieved.
"I am totally prepared to walk. It could happen. Maybe it won't be necessary. I hope it won't be necessary to walk, because I really believe that Kim Jong-un wants to do something that is going to be great for his people, and also great for his family, and great for himself," Trump said.
"I am totally prepared to walk away. I did it once before. You have to be able to walk away. If you're not going to be able to walk away -- we didn't walk away from the horrible Iran deal that was signed, and if you look at what's happened, since I signed that deal, Iran and in all fairness, I say it with great respect for the people of Iran, but Iran is acting a lot differently. They're no longer looking so much to the Mediterranean," he said.
Iran, he said, is no longer looking so much to what was going on in Syria, Yemen and other places.
"They're a much different country over the last three months. And again, I say that with hope that maybe something can happen," said the US President.