Updated at 10:43 p.m. ET Wednesday 5/29
(CNN) - The U.S. State Department helped Sen. John McCain with his trip into war-torn Syria this week, the senator from Arizona said Wednesday.
McCain acknowledged on CNN's "Anderson Cooper 360" that the State Department and rebel groups were both involved in providing his security.
"I want to express my appreciation to the State Department," McCain said in the exclusive CNN interview. "The reality is if they had said no, I wouldn't have made this visit. They were very helpful and cooperative, and I'm grateful."
On Monday, McCain slipped across the Syria-Turkey border and became the first U.S. senator to visit the country since civil war broke out more than two years ago. He traveled roughly 1 kilometer inside Syria to meet with rebel leaders from different Syrian cities. He remained in the country for several hours.
State Department Spokeswoman Jen Psaki confirmed earlier Wednesday in the daily briefing that Secretary of State John Kerry knew beforehand McCain intended to travel to Syria. While she said Kerry and McCain spoke about his trip Tuesday evening, she directed reporters to the senator's office for any further questions.
The White House was also aware of McCain's travel plans, Press Secretary Jay Carney said this week.
McCain declined to give too many details on the logistics of his trip but said the D.C.-based Syrian Emergency Task Force help set up the meetings with rebel groups. He credited Syrians for being "pretty brave in making this happen."
He did not detail how exactly the State Department helped him with security but said Salim Idris, a Syrian rebel general, accompanied him in and out of Syria from Turkey.
McCain is the leading voice in Congress for a greater U.S. role in ending Syria's civil war, which has been waged for more than two years. He has suggested establishing "safe zones" for Syria's rebels and taking out the regime's air assets, along with providing lethal weapons to Syria's opposition.
Meeting members of Syria's opposition face-to-face in the country they're fighting to control deepened his conviction that the United States must become further engaged in the bloody conflict.
The 2008 GOP presidential nominee said meeting 18 commanders with the Free Syrian Army provided an in-the-flesh reminder of the civil war's human cost.
"When you look at the faces of these people and hear their stories, so many of them have lost family members, so many of them have lost friends," McCain said in the interview, speaking from Dubai. "This is a pretty bloody, bloody business that they've been in."
He said Wednesday his positions have hardened now that he's seen the fighters working to oust Syrian President Bashar al Assad.
"Of course it's as you might imagine intensified because these are human beings that are trying to achieve the same thing that we have shed American blood and treasure for, for well over 200 years," he said.
Republicans and Democrats alike have called on President Barack Obama to ramp up support for Syrian rebels, who now receive nonlethal aid like food and medicine from the United States. In early April that aid was stepped up to include equipment such as body armor, night vision goggles and other military equipment that is considered defensive in nature.
In their meeting with McCain, leaders of the Syrian rebel forces pressed the United States to provide them with weapons to continue their fight against Assad. They specifically said they need ammunition, as well as antitank and antiaircraft weapons, McCain said.
"They do not understand why we won't help them," he said.
They also called for the United States to "take greater leadership in supporting the rebels in a more serious manner," according to Mouaz Moustafa, who helps run the group that organized McCain's trip.
"Their main message was that we are desperate for ammunition. We are desperate for weapons," Moustafa said.
U.S. officials from both parties have expressed concerns about American arms ending up in the hands of terrorists in Syria should the United States decide to provide rebels with lethal aid. Members of al-Nusra Front, which is designated by the United States as a pro-al Qaeda terrorist group, have joined the rebels in their fight against Assad.
Republican Sen. Rand Paul, for example, has been outspoken about his opposition to U.S. intervention in Syria. In a new opinion piece for CNN.com, Paul writes that arming the rebels would be "complicated and dangerous" and "could actually help the extremists."
He also took subtle jabs at McCain, pointing to the senator's switch in support from former Libyan leader Moammar Gadhafi to the rebels seeking his demise.
McCain told CNN that members of the extremist group represent only 7% of the 100,000 total rebel forces. "We can help the right people," he said. "Is there some risk involved? Absolutely. But is the status quo acceptable?"