Vice President Dick Cheney issued a warning to Iran while aboard an aircraft carrier in the Persian Gulf on Friday, saying the United States would join allies to keep Iran from getting nuclear weapons "and dominating the region."

With two U.S. carrier groups now in the region, the vice president declared, "We're sending clear messages to friends and adversaries alike. We'll keep the sea lanes open."

Iran exerts considerable control over the narrow passageway that separates the Persian Gulf from the open waters of the Arabian Sea. Roughly a quarter of the world's oil supplies pass through the Straits of Hormuz.

Iran loomed about 150 miles to the east as Cheney spoke aboard the USS John C. Stennis. The carrier was steaming about 20 miles off Abu Dhabi in the United Arab Emirates. Cheney is spending time there after a two-day tour of Iraq.

It was the latest shot in an escalating war of words, with both Tehran and Washington seeking to increase influence over states bordering Iraq. Cheney's visit comes just two days before Iranian President Mahmoud Ahmadinejad was to visit Abu Dhabi.

"We'll stand with others to prevent Iran from gaining nuclear weapons and dominating this region," said Cheney.

Both Shiite-dominated Iran and Saudi Arabia, with a predominantly Sunni Muslim population, are vying for influence among their respective ethnic factions in Iraq. Cheney visits Saudi Arabia on Saturday as part of his tour of moderate Arab states, seeking help in stabilizing Iraq. He also will visit Egypt and Jordan.

It was a repeat visit for Cheney, who came to the carrier in March 2002 as he was trying to build support in the area for invading Iraq.

Standing in front of five F18 Super Hornet fighters and a huge American flag in the cavernous hangar deck — one flight below the carrier's flight deck — Cheney sounded a hard line both on holding firm in Iraq and confronting Iran if necessary.

Little more than four years after President Bush stood on another aircraft carrier beneath a "Mission Accomplished" banner and declared an end to major combat, Cheney gave a far more measured description of progress in Iraq.

"We want to complete the mission, get it done right, and return with honor," he told Stennis crew members.

Officials said that between 3,500 and 4,000 of the carrier's 5,000 sailors and Marines stood in sweltering heat — hovering over 100 degrees — to hear Cheney speak.

"It's not easy to serve in this part of the world. It's a place of tension and many conflicts," said Cheney.

"We'll stands with our friends in opposing extremism and strategic threats. We'll disrupt attacks on our own forces," Cheney said. U.S. officials have said that some of the sophisticated roadside bombs used against U.S. troops in Iraq have come from Iran.

Cheney flew to and from the carrier by helicopter.