WATCH: Hegseth won't say if U.S. will send ground troops into Iran

Defense Secretary Pete Hegseth declined to tell reporters Tuesday whether or not the U.S. military will deploy ground troops against Iran.

"You can't fight and win a war if you tell your adversary what you are willing to do or what you are not willing to do to include boots on the ground," he said.

WATCH: Iran hits Israeli oil refinery as Trump escalates threats in widening regional war

Hegseth added: "Our adversary right now thinks there are 15 different ways we could come at them with boots on the ground. And guess what? There are."

Hegseth also said talks with Iran to end the conflict are ongoing.

WATCH LIVE: UN Security Council meets for emergency session on peacekeepers killed in Lebanon

"We don't want to have to do more militarily than we have to," he said. "But I didn't mean it flippantly when I said, in the meantime, we'll negotiate with bombs."

Hegseth says he visited U.S. troops fighting in Iran war

Speaking at a news conference from the Pentagon on Tuesday, Hegseth said he visited American service members in the Middle East. He said he wouldn't disclose the base names or locations for operational security.

Hegseth said he visited areas under the responsibility of U.S. Central Command on Saturday for about half a day.

WATCH: Leavitt says U.S. troops appreciate prayers after Pope Leo speaks out against waging war

"Suffice it to say, the trip was an honor," Hegseth told reporters. "I had a chance to bear witness, and I witnessed the best of America."

Gen. Caine says U.S. strikes are focused on Iranian naval targets and defense industrial sites

Speaking at the news conference, Gen. Dan Caine, chairman of the Joint Chiefs of Staff, said U.S. military action in Iran remains focused on "targeting their minelaying capability, their naval assets."

"We've taken out again more than 150 ships," Caine said, adding that attack helicopters are now joining in the effort targeting Iranian naval targets.

READ MORE: Kharg Island is key to Iran's oil exports. Targeting it carries major risks

Another key objective of the war is disabling Iran's defense industrial base, including nuclear research sites, Caine said.

"This includes factories, warehouses, nuclear weapons research and development labs, and the associated infrastructure required for Iran to reconstitute its combat capability," Caine said.

If countries don't stand with you, it's not much of an alliance, Hegseth says

The defense secretary said the U.S. undertook the war in Iran for the "free world" and questioned the value of the NATO alliance if those countries don't stand with America.

Hegseth pointed to a social media post from President Donald Trump about allies and said Iranian missiles don't reach the U.S. but could hit allies and others.

WATCH: At Pentagon Christian service, Hegseth prays for violence 'against those who deserve no mercy'

"The president's pointing out you don't have much of an, an alliance if you have countries that are not willing to stand with you when you need them," Hegseth said.

Hegseth says Britain and other allies should 'step up' to open the Strait of Hormuz

"There are countries around the world who ought be prepared to step up on this critical waterway as well," Hegseth said. "It's not just the United States Navy. Last time I checked, there was supposed to be a big, bad Royal Navy that could be prepared to do things like that as well."

READ MORE: Spain closes airspace to U.S. planes involved in Iran war

In a social media post Tuesday, Trump said nations upset by high fuel prices should "go get your own oil" as as average U.S. gas prices shot past $4 a gallon.