June 2 (UPI) — Secretary of State Marco Rubio told the Senate on Tuesday morning that Iran must reopen the Strait of Hormuz and commit to future talks on its nuclear program before the United States will make concessions.

He testified before the Senate Foreign Relations Committee before a scheduled afternoon meeting with a House panel on State Department spending. Both sessions were planned so that Rubio could defend the department’s nearly $36 million budget request for the 2027 fiscal year.

Rubio is also President Donald Trump’s national security adviser.

The Washington Post reported that Rubio’s testimony with lawmakers has been mostly friendly. He served in the Senate for 14 years and in the House for 8, representing Florida.

Lawmakers from both sides of the aisle have expressed frustration with the cost and potential political fallout from the war with Iran.

“This war and the administration’s decision to blockade has now held the entire world economy, and the U.S. economy, hostage to the ability to negotiate an agreement with Iran,” said Sen. Chris Murphy, D-Conn, The Post reported.

The Strait of Hormuz, which has been closed by Iran since late February, must reopen, Rubio stressed. The strait is a critical waterway for shipping of much of the world’s oil, gas and fertilizer. The closure has caused gas prices to rise, causing anxiety as Republicans fear losing House and Senate seats in November.

Rubio said Trump demands that Iran enter into negotiating “severe and long-term limitations” on its nuclear program, including disposing of enriched uranium, and those talks could take months.

But he said he’s optimistic that Iran is more willing to negotiate on nukes.

“They have agreed to negotiate aspects of their nuclear program that just a month ago, just a year ago, they were refusing to even mention,” The Guardian reported Rubio said. He warned that it’s “not a guarantee that ultimately it will lead to a deal that’s acceptable,” and Iran’s leadership instability has made the negotiations more difficult.

Rubio said Iran had intended to use its conventional weapons capabilities as a “shield” to protect its nuclear program, The Guardian reported.

“What they tried to do is, they were going to try to build a conventional shield and hide behind that conventional shield,” he said, explaining why Trump wanted to start the war.

He also admitted, after questioning by Sen. Ted Cruz, R-Texas, that another sticking point for Trump was that Iran stop supporting terrorist proxy groups. He said Trump is not willing to ease sanctions just for opening the strait.

Rubio said that Iranian Ayatollah Mojtaba Khamenei is believed to be alive.

“I would imagine, given what’s happened to multiple leaders in that system, being very public is probably not something that’s recommended for them internally,” he said. “But that said, I think there are indications out there that he is increasingly engaging at some level, although all of his communications have been in writing and through intermediaries.”

Along with Iran, lawmakers were expected to ask Rubio about the president’s comments about Cuba and Taiwan.