​Defense Secretary Jim Mattis on Thursday said the US is still looking for “actual evidence” of a chemical weapons attack in Syria, but United Nations Ambassador Nikki Haley said the United States has “enough” proof.

“I believe there was a chemical attack and we are looking for the actual evidence,” Mattis told ​a hearing of the House Armed Services Committee, adding that he wants inspectors in Syria “probably within the week.”

But Haley said she’s satisfied and urged caution in the US’ response to the chemical weapons attack Saturday in Douma that killed at least 60 people.

“We definitely have enough proof, but now we just have to be thoughtful in our action,” ​she told MSNBC. “The national security team is trying to give him [President Trump] as many options as we can, and we’ll be thoughtful about it and see what happens.”

​Mattis said the US did not have any personnel on the ground in Douma during the attack and that ​time is of the essence to gather evidence.

“As each day goes by — as you know, it is a non-persistent gas — so it becomes more and more difficult to confirm it,” Mattis told the lawmakers.

Still, he said the attack was “inexcusable, beyond the pale, and in the worst interest of not just the chemical weapons convention, but civilization itself.”

​At the White House, Trump said he has been in and out of meetings all day about the situation in Syria​.​

“We’re looking very, very seriously, very closely at that whole situation, and we’ll see what happens, folks. We’ll see what happens. It’s too bad that the world puts us in a position like that,” he said​.

“Now we have to make some further decisions. So they’ll be made fairly soon.”