Ahead of U.N. meetings, Trump aides call for more pressure on North Korea

David Jackson | USA TODAY

Show Caption Hide Caption Trump mocks Clinton, Kim Jong Un in tweetstorm President Trump fired up Twitter Sunday morning with tweets on Kim Jong Un and Hillary Clinton.

NEW YORK — President Trump and top aides warmed up for this week's series of United Nations meetings by calling for more global pressure on North Korea and to at least talk about global efforts to address climate change.

After a late-night phone call between Trump and South Korean President Moon Jae-in, the White House said the two leaders will meet at the U.N. and remain "committed to continuing to take steps to strengthen deterrence and defense capabilities and to maximize economic and diplomatic pressure on North Korea."

In tweeting about the call with Moon, Trump referred to North Korean leader Kim Jong Un as "Rocket Man" and appeared to refer to economic sanctions by saying that "long gas lines forming in North Korea. Too bad!"

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Meanwhile, National Security Adviser H.R. McMaster said during Sunday show interviews that new stories suggesting Trump has changed his mind about the U.S. withdrawal from the Paris climate change agreement are false. But he added that the administration is open to discussing the issue.

"He's open to any discussions that will help us improve the environment, that will help us ensure energy security and will advance our prosperity and the prosperity of American workers and American businesses," McMaster said on ABC's This Week.

North Korea's nuclear threats and climate change are among the main topics as Trump makes his first appearance as president at the United Nations General Assembly. The president is scheduled to address the assembly Tuesday and to meet separately with other world leaders throughout the week.

Trump plans to ask U.N. members, particularly China, to help pressure North Korea into giving up nuclear weapons and to stop threatening to use them.

While Trump has questioned the effectiveness of existing sanctions, U.N. Ambassador Nikki Haley told CNN that North Korea "is already starting to feel the pinch. That’s the reason you seeing them reacting the way they are."

Despite longtime criticism from Trump, Kim's government in recent months has threatened U.S. facilities in Guam, fired two missiles over Japan and tested a hydrogen bomb.

Speaking on CNN's State of the Union, Haley said that while the United States seeks a diplomatic solution in North Korea, it is also prepared to use a military option under the leadership of Defense Secretary Jim Mattis.

"If the United States has to defend itself or defend its allies in any way, North Korea will be destroyed," she told CNN.

If diplomacy doesn't work, Haley said, "General Mattis will take care of it."

Some United Nations members, in the meantime, want Trump to reconsider his decision to withdraw the United States from the Paris climate change agreement reached by the Obama administration. A news report over the weekend said Trump was considering that option, but administration officials denied it.

The Paris deal puts more demands on the United States than on other countries when it comes to cutting carbon emissions, McMaster said. He noted that when Trump made his announcement in June about withdrawal, he said he was open to talk about a revamped agreement.

"He's out of the Paris climate record, but he says the door is open," McMaster told Fox News Sunday.

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The topic of terrorism is also likely to surface at the United Nations, especially in light of Friday's attack in a London subway train.

On ABC, McMaster echoed a Trump tweet calling for a tougher travel ban into the United States, saying "this is something we're looking at."

The administration's current ban, affecting travel from six Muslim-majority countries, is the subject of legal challenges.

While opponents describe the ban as an unconstitutional religious test, McMaster said it is a "first step" toward improved border screening designed to weed out potential terrorists.

"If you can't screen people effectively to know who's coming into your country, then you shouldn't allow people from that country to travel," McMaster said.

Trump's political opponents pointed to what they called a series of mixed messages on national security, the environment and border security, as well as other issues.

Rep. Adam Schiff, D-Calif., speaking on ABC, cited Trump's changed positions on what to do about the status of children brought into the United States illegally by their parents, a group known as the DREAMers.

"It's very difficult to tell day-to-day what the administration intends with climate, with the DREAMers, and any host of other issues," Schiff said.