The United States has warned it could target Iran’s nuclear infrastructure and restart full-scale combat operations if Tehran refuses to agree to a peace deal, as Washington tightens a sweeping naval blockade in the Strait of Hormuz.

US forces in the Middle East are “postured to restart combat operations immediately,” top American military officials said on Thursday, underscoring the risk of rapid escalation.

Defence Secretary Pete Hegseth said the blockade, now in its fourth day, would continue indefinitely as part of efforts to pressure Iran.

“The United States will block all shipping to and from Iranian ports in the Strait of Hormuz for ‘as long as it takes,’” he said.

“Let me be clear, this blockade applies to all ships, regardless of nationality,” Hegseth told a news briefing.

“For as long as it takes, we will maintain this blockade.”

Addressing Iran directly, he said: “You Iran, can choose a prosperous future, a golden ⁠bridge, and we hope that you do for the people of Iran.”

“But if Iran chooses poorly, then they will have a blockade and bombs dropping on infrastructure, power and energy.”

Hegseth warned of a sharp military imbalance, saying: “this is not a fair fight, ⁠and we know what military assets you are moving and where you are moving them to.”

He added that Washington was closely monitoring Iranian movements and operating at heightened readiness, with only a fraction of US forces currently deployed.

General Dan Caine, chairman of the Joint Chiefs of Staff, said US forces were “ready to resume major combat operations at literally a moment’s notice.”

He said US Navy ships would pursue any Iranian-flagged vessel or those providing material support to Iran, with enforcement extending across Iranian territorial waters and international waters.

Ships attempting to breach the blockade would be intercepted and warned that “If ⁠you do not comply with this blockade, we will use force”.

Caine said the objective of the operation was to choke Iran’s oil exports and disrupt its maritime activity.

“The blockade applies to all vessels heading to Iranian ports,” he said, adding that 13 ships had already turned back rather than risk confrontation.

He noted that no vessels had been boarded so far, but said the blockade had effectively halted Iranian exports.

Caine added that military rules would be enforced across Iranian maritime zones, while US forces remained ready to launch strikes “at a moment’s notice.”

Hegseth said the United States could escalate further if Iran failed to reach an agreement, including targeting its nuclear infrastructure to reopen shipping lanes.

He also defended the operation as sustainable, saying Washington could maintain control of the strategic waterway for as long as required.

The Trump administration has expressed optimism about a potential deal but warned that economic and military pressure would intensify if Iran remains defiant.