Republican presidential front-runner Donald Trump criticized President Barack Obama on Monday for putting too much focus on curbing climate change while ignoring more serious problems like North Korea.

In an interview with MSNBC, Trump said it was "one of the dumbest statements I've ever heard in politics" for Obama to say that "our No. 1 problem is global warming."

Obama was in Paris for a crucial U.N. conference aimed at working out a deal on curbing climate change.

"When we have large groups of people that want to blow up every one of our cities, that want to destroy our country, that want to kill our people, and he's worried about global warming," he said.

"I think it's one of the dumbest things I've ever seen, or perhaps most naive. He could be naive in a certain way."

The billionaire real estate mogul said that North Korea "is never even mentioned" and criticized the Obama administration for clinching "one of the worst deals in history" with Iran.

"But Iran probably doesn't have nuclear weapons right now. But what about North Korea? Nobody mentions that. That's like when you have something that you don't want to do, you don't mention it because you sort of don't want to do it, you don't want to talk about it," he said.

North Korea has conducted three underground nuclear tests so far, in 2006, 2009 and 2013. The country has also conducted a series of long-range missile or rocket launches and experts have warned that it is only a matter of time until the North develops nuclear-tipped missiles.

Observers have said that North Korea stands low in the U.S. priority list and that the Obama administration has little interest in resuming nuclear negotiations with Pyongyang as it has been preoccupied with Middle East issues, such as Iran's nuclear program and the militant group Islamic State. (Yonhap)