Vice President Mike Pence on Sunday doubled down on President Donald Trump's response to Iran military forces that shot down a US Navy drone, saying there was still confusion surrounding the attack.

Though he said on CNN's "State of the Union" that US intelligence was "not convinced that it was authorized at the highest levels," Pence said, "all options remain on the table" for a forceful US response.

Trump seemed to issue mixed responses in the days following the attack and drew criticism for his response, which Pence waved off Sunday.

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Vice President Mike Pence has doubled down on President Donald Trump's mixed response to Iran military forces that shot down a US Navy drone.

"The president also had doubts as to whether or not the downing of our unmanned aircraft was actually authorized at the highest levels," Pence said, echoing Trump's comments from the past few days.

"We're not convinced that it was authorized at the highest levels," Pence finished, before telling Tapper he couldn't comment further on US intelligence on the incident.

—State of the Union (@CNNSotu) June 23, 2019

The vice president's comments come as the latest response from the administration that sparked concerns for possibly being too weak. Republican Sen. Lindsey Graham tweeted on Friday that he appreciates "the difficult decisions" the president has to make, but said, "when it comes to the Middle East, people rightly talk about the 'Cost of Action' but they seldom mention the 'Cost of Inaction.'"

The lawmaker later added that "in some instances, failing to act can prove to be the most dangerous choice of all."

Read more: 'Let's make Iran great again': After calling off Iran strike, Trump said he would be the country's 'best friend' following future nuclear deal

Trump said Friday that though he was "cocked & loaded," he decided against a strike because it would cause too many deaths. Pence echoed this explanation, saying Sunday that Trump "concluded that it was not a proportionate response to shooting down an unmanned American aircraft."

The vice president rejected the notion that the president's response was too subtle, telling Tapper that "all options remain on the table."

Speaking just a day after he called off the strike, Trump told reporters at the White House he was looking forward to next steps in US relations with the country after "getting praise" for his decision to pull back the strike.

Trump also said the attack was "probably intentional," a firm development after he had seemed to waver on his dealings with the country earlier in the week, saying the day after the attack that it was "a mistake" and that he found it "hard to believe" the attack was "intentional" while only offering vague answers about whether he would pursue war with Iran.

Maj. Gen. Hossein Salami, the commander of the elite military unit that reports to Iran's supreme leader, issued a clearer account of the country's actions, saying there was "a clear message" that Iran would strike back against any US aggression.

"Borders are our red lines and any enemy which violates them will not go back home and will be annihilated. The only way for enemies is to respect Iran's territorial integrity and national interests," Salami, the commander of the Islamic Revolutionary Guard Corps (IRGC), was quoted as saying by Iran's Fars news agency.