Sen. Bob Corker, R-Tennessee, suggested Sunday that President Trump's tweets taking aim at North Korea are undermining diplomatic efforts regarding the country and its surrounding region.

"When our Secretary of State is sitting down with a partner that matters most, China, trying to negotiate something that would resolve and keep us from going into military conflict with North Korea which brings in South Korea, Japan, China, and Russia, and he's kneecapped by the president, it hurts our nation. It hurts our efforts," Corker said Sunday on "Face the Nation."

Corker called China our "greatest partner" when it comes to North Korea, and said "every military leader wants the State Department and our Secretary of State to be successful" in exercising diplomacy to "keep our men and women in uniform out of harm's way."

When Tillerson is "kneecapped" by Mr. Trump "it leads us more fully towards the conflict that most of us would like to see resolved in another way," Corker said.

"The tweets that are sent out mocking a leader of another country raises tensions in the region," he said. "And so if people are sitting there, they know they've got an erratic leader in North Korea, they've lived with three erratic leaders. And then when we start exhibiting some of those same tendencies, it creates an air that leads again more fully towards conflict."

The senator, who is chairman of the Senate Committee on Foreign Relations and one of Mr. Trump's toughest critics within the Republican Party, previously told The New York Times that threats like those lobbed by the president toward other countries such as North Korea would set the U.S. "on the path to World War III."

Corker said on "Face the Nation" that "what we need to be doing" is supporting the efforts of Tillerson and Defense Secretary James Mattis when it comes diplomacy.

His newest comments came just days after Corker spoke out against the president on Tuesday -- the same day Mr. Trump lunched on Capitol Hill with his Republican colleagues in an effort to push the administration's tax plan. Corker told reporters on the Hill that the president would be remembered for "the debasing of our nation," and would not able to bring his conduct up to the level demanded by the presidency.

"I think that he's proven himself unable to rise to the occasion, and I think many of us, me included, have tried to, you know, intervene, and I have had a private dinner and have been with him on multiple occasions to try and create some kind of aspirational approach, if you will, to the way that he conducts himself. I don't think that that's possible. He's obviously not going to rise to the occasion as president," said Corker.

While Corker has announced he will no longer be seeking re-election in 2018, he said that he, along with his Senate colleagues, are just "trying to do the best job we can."

"I care deeply about our country. It's why I ran for the Senate. I care even more deeply about it now having been there 11 years. I've been in the foreign relations area the entire time I've been there," said Corker.

He added, "I'm chairman. I have coffees with Tillerson often. I talk with him. I talk with national security folks not only here, but around the world. And I have a good sense of what is happening. I'm just speaking to that. That's my job. And I'll continue to do so."