"If there’s an agreement that benefits the American people, certainly," McMaster told ABC News Chief Anchor George Stephanopoulos in an interview on "This Week" Sunday.
In June, the president announced that the U.S. would exit the climate agreement, saying, "“I was elected to represent the citizens of Pittsburgh, not Paris."
Trump’s national security adviser said the president has been clear he is withdrawing the U.S. from the deal because it does not benefit the U.S., but would be open to re-entering the accord if there is a better deal.
“What the president has said is that we are withdrawing from the Paris Accord. He left the door open to re-entering at some later time if there can be a better deal for the United States,” McMaster said on “This Week.”
“The president’s objection to Paris is not that he’s against the environment or the climate,” McMaster said. “What the president wants is a more effective approach to energy and the climate.”
McMaster was also asked about the president's response to the London Underground terror attack Friday. After the attack, the president tweeted that the United States' travel ban should be "far larger, tougher."
McMaster said the administration is "looking at" the issue.
"This is something that we're looking at ... how to protect the American people better, how to ensure that we know who these people are who are moving," he said. "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 also addressed North Korea's latest missile test and the UN Security Council's approval of new sanctions against the regime. The president on Sept. 12 called the sanctions "not a big deal," apparently questioning their potential effectiveness.
"We all have our doubts about whether or not that's going to be enough," McMaster said of the UN action. "And so we have to prepare all options. We have to make sure all options are under development to ensure that this regime cannot threaten the world with a nuclear weapon," he said.
Trump tweeted this morning that he spoke with South Korean President Moon Jae-in last night and asked, "how Rocket Man is doing. Long gas lines forming in North Korea. Too bad!"
Stephanopoulos asked McMaster if "Rocket Man" refers to North Korean leader Kim Jong Un.
"It appears to be so. That is where the rockets and missiles are coming from, is North Korea," he responded.