Washington (CNN) A high-level American delegation tasked with brokering a ceasefire amid the Turkish incursion into Syria landed in Turkey Thursday morning to negotiate, but President Donald Trump's recent comments have undercut their mandate, critics say.

The high-level US delegation includes Vice President Mike Pence, Secretary of State Mike Pompeo and national security adviser Robert O'Brien.

The group is expected to meet with Turkish President Recep Tayyip Erdogan to address the situation in Syria , marking the first major meeting between the two countries since Trump pulled US armed forces out of northern Syria. The pullback is widely seen as giving Erdogan room to act on his long-held goal of attacking the Kurds who fought for and with the US against ISIS.

Before meeting with the larger delegation, Pence and Erdogan are expected to sit down one-on-one.

The key objectives for Thursday's meeting remains unclear, but earlier Wednesday, Pompeo voiced optimism about the prospects of a deal to halt the ongoing Turkish military operation.

"I'm very hopeful we can get a good resolution when the vice president and I travel later today and are on the ground there maybe 24 hours from now," Pompeo said during an appearance on Fox Business.

The US has been talking about getting tough with Turkey, but they have not actually applied another key sanction other countries have used in the past -- cutting off arms sales.

It's also unclear whether the delegation can get Turkey to reach a ceasefire. Speaking to journalists traveling on his presidential plane following a visit to Azerbaijan on Tuesday, Erdogan said a ceasefire was off the table.

"Declare a ceasefire, they say. We will never declare a ceasefire," Erdogan said. "We do not sit at the table with terrorist organizations."

Erdogan also said that he's not worried about American-imposed sanctions.

At one point this week, Erdogan also said he would only meet with Trump -- not the delegation. But by Wednesday, Erdogan said he would meet with the group.

Trump prefaced the Turkey trip with a series of statements on Wednesday indicating that he not only wants the US to be less involved in the region, but he wants other, non-allied stakeholders, including Iran, Russia, and Syria, to become more involved.

Trump also defended withdrawing troops from northeastern Syria by saying that sanctions on Turkey are more effective at maintaining stability between the Turks and Kurds.

The President also asserted Wednesday that Turkey's incursion of northern Syria "has nothing to do with us" and added that former US allies -- the Kurds -- are "not angels."

"Our soldiers are not in harm's way, as they shouldn't be, as two countries fight over land that has nothing to do with us," Trump said during an Oval Office meeting with Italian President Sergio Mattarella.

But other world leaders (including Mattarella), former members of Trump's own administration, and key congressional Republicans, have all voiced their opposition to Trump's strategy in Syria with Turkey.

Republican Sen. Lindsey Graham called the Syria decision the " biggest mistake " of Trump's presidency.

"The statements by President Trump about Turkey's invasion being of no concern to us also completely undercut Vice President Pence and Secretary Pompeo's ability to end the conflict," Graham, who at times has been a close ally to Trump, tweeted.

Senate Majority Leader Mitch McConnell said he thought the decision to pull out of northern Syria was a mistake.

"I have concerns about this particular decision, I think it was a mistake, I hope it can be repaired," McConnell said of the US-Kurdish alliance.

Former Secretary of Defense James Mattis also warned ISIS would have a resurgence if the US does not keep the pressure on in Syria.

Trump outwardly appeared unconcerned, dismissing Graham's comments in a press conference Wednesday afternoon by saying the South Carolina senator "would like to stay in the Middle East for the next thousand years."

And during a meeting with congressional leadership, the President was asked about Mattis' warning, according to a Democratic source familiar. Trump responded by saying that Mattis was "the world's most overrated general."

"You know why? He wasn't tough enough. I captured ISIS. Mattis said it would take two years. I captured them in one month," Trump said, according to the source.

This story has been updated with additional developments on Thursday.