President-elect Donald Trump quipped on Tuesday that his choice for secretary of state, Rex Tillerson, is finding his Senate confirmation tougher than his days as chief executive officer of Exxon Mobil, when he could cut deals with foreign nations.

Trump and Vice President-elect Mike Pence appeared together at a VIP dinner featuring nearly 150 diplomats from countries around the world along with U.S. lawmakers and members of the Trump White House who will take power on Friday.

"I think it's tougher than he thought," Trump told the crowd, noting that Tillerson was in attendance. "He goes into a country, takes the oil, goes into another country. It's tough dealing with these politicians, right? He's going to be so incredible."

Tillerson has faced tough questions from some senators about his warm ties to Russia as a top U.S. oil executive. Sen. Marco Rubio of Florida, a Republican, has said he might vote against Tillerson.

At the black-tie dinner, both Trump and Pence sought to reassure countries that might be concerned about the "America first" agenda they plan to pursue, which could lead to rewriting the NATO alliance and trade deals.

"The truth is — and this may be news to many of you — but I'm not sure that the national media here in America completely understands the president-elect," Pence said in introducing Trump.

"He's going to stand tall on the world stage," Pence added. "Donald Trump will be a president who puts American first, but we will work every day with nations around the world to advance the peace and prosperity of our allies and our friends across the world."