Muscat, Oman (CNN) - The US commander who has been leading the war against ISIS told CNN Friday that he disagreed with Donald Trump's decision in December to pull troops out of Syria and warned that the terror group was far from defeated, in a stark difference of opinion with the President.
Joseph Votel, the top American general in the Middle East, also said that the US-backed forces on the ground in Syria were not ready to handle the threat of ISIS on their own.
"It would not have been my military advice at that particular time ... I would not have made that suggestion, frankly," Votel said of the troop withdrawal announcement. "(The caliphate) still has leaders, still has fighters, it still has facilitators, it still has resources, so our continued military pressure is necessary to continue to go after that network."
Votel, speaking to CNN from Oman on Friday, revealed he would only have declared that ISIS had been defeated, as Trump did in December, if he was sure they no longer posed a threat.
"When I say, 'we have defeated them,' I want to ensure that means they do not have the capability to plot or direct attacks against the US or our allies," Votel said. "They still have this very powerful ideology, so they can inspire."
The commander of US Central Command had previously said that he "was not consulted" before Trump's controversial announcement late last year that the US would rapidly withdraw its troops from the war-torn country.
Trump's announcement appalled US lawmakers and triggered resignations, including that of Defense Secretary James Mattis and the senior State Department official in charge of the anti-ISIS campaign.
On Friday, Votel also said that the US-backed Syrian Democratic Forces (SDF) -- who launched an offensive to oust ISIS from its only remaining enclave in Syria last weekend -- could not defeat the terror group without continued American assistance.
"They still require our enablement and our assistance with this," Votel said, adding that the US military was still in the midst of executing a "well-crafted military campaign."
"We want (ISIS) to be able to be controlled or addressed by the indigenous partners, whether that's the Iraqi security forces in Iraq, or the Syrian Democratic Forces in Syria, that when they are capable of handing this threat on their own, without our assistance, that will be another key criteria indicating to me that we have accomplished our mission of defeat of ISIS."
Concern over Iran's 'ability to innovate'
Votel also said Iran posed a growing threat to US partners in the region and expressed concern over its development of advanced weapons, though he acknowledged that Tehran had held up its side of the nuclear deal that Trump withdrew from last year.
"I acknowledged that the reporting is that they remain in compliance with the provisions of the JCPOA [the nuclear deal], but of course we do see them continuing to advance their missile technology," Votel said. "It should not be lost on anybody that an advanced ballistic missile program could also be used to move weapons of mass destruction."
"Their ability to be innovative, their ability to seek more precision, and the fact that they are increasing their quantity are the greatest areas of concern for me," he added.
"They are looking to use new ways of orchestrating their actions so it isn't so much so through just ballistic missiles, but we've also seen a proliferation of unmanned aerial systems ... that operate in different (ways), so this could challenge us."
Unmanned surface systems, which can include explosive boats designed to target enemy vessels, have concerned US officials for some time, particularly after Iranian-backed Houthi rebels based in Yemen used such a boat to attack a vessel that belonged to Saudi Arabia. The US has accused Tehran of supplying the Houthis with these boats.
Vice Adm. James Malloy, the commander of US Naval Forces Central Command, voiced similar concerns to Votel on Thursday, telling CNN that Iran is in possession of improved and dangerous weapons systems.
Votel's comments come a day after Vice President Mike Pence called on a gathering of 62 countries in Poland to confront Iran directly, and ripped into Europe for its refusal to pull out of the nuclear deal.
Votel also acknowledged concerns after a CNN investigation, published earlier this month, that revealed Saudi Arabia and its coalition partners had transferred American-made weapons to al Qaeda-linked fighters, hardline Salafi militias and other factions waging war in Yemen. The weapons, CNN revealed, had also made their way into the hands of Iranian-backed rebels, exposing some sensitive US military technology to Tehran.
"We are always concerned about US equipment falling in the hands of our adversaries, our competitors out there," he told CNN Friday.
"In terms of ... how those things are monitored is under investigation, that actually falls under the Department of State, so I understand that the appropriate offices are looking at that now and hopefully we'll have an answer."
This story has been updated.