"We'll keep the sea lanes open," Cheney said from the hangar deck of the USS John C. Stennis as it steamed about 150 miles from the Iranian coast.
Cheney is touring the Middle East asking Arab allies to do more to help Iraq and to curb Iran's growing power in the region. With Iraq in turmoil, both Iran and Saudi Arabia are maneuvering to see who can help fill the leadership vacuum.
The vice president made clear the United States' intentions on the rivalry. "We'll stand with others to prevent Iran from gaining nuclear weapons and dominating this region," he said.
On Saturday, Cheney will make a fence-mending visit to Saudi Arabia.
The oil-rich kingdom, long a key American ally in the Middle East, recently has been shunning the U.S.-supported government of Iraqi Prime Minister Nouri al-Maliki, suggesting he is too close to Iran.
Roughly a quarter of the world's oil supplies pass through the narrow Straits of Hormuz connecting the Persian Gulf with the open waters of the Arabian Sea. Iran controls the eastern side of the straits.
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."
The carrier was in the Gulf about 20 miles off Abu Dhabi in the United Arab Emirates. Cheney is spending time there after a two-day tour of Iraq.
Standing in front of five F/A-18 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.
Just over four years after President Bush stood on another aircraft carrier beneath a "Mission Accomplished" banner and declared an end to major combat, Cheney had a far more subdued message.
"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 stand with our friends in opposing extremism and strategic threats. We'll disrupt attacks on our own forces," he added. U.S. officials have said that some of the sophisticated roadside bombs used against U.S. troops in Iraq have come from Iran.
After returning from the carrier, Cheney had dinner with Emirates Crown Prince Sheik Mohammed bin Zayed Al Nahyan.
On Saturday, before leaving for Saudi Arabia, Cheney is expected to press Emirates President Sheik Khalifa bin Zayed Al Nahyan to support U.S. efforts in Iraq and to shut down Iranian companies in his country that U.S. officials believe are backing Iran's nuclear development.
Some 500,000 Iranians live in the Emirates.
Cheney's visit comes just two days before Iranian President Mahmoud Ahmadinejad is to visit Abu Dhabi.
Ahmadinejad wants the Emirates and other Gulf Arab countries to drop their military alliances with Washington and join Iran in regional efforts. The United States has about 40,000 troops on land bases in Gulf countries outside Iraq and about 20,000 sailors and Marines in the region.
No Gulf state has yet backed Iran's offer of an alliance.
Iran's top nuclear negotiator said Friday that a compromise over its nuclear program was impossible if the West continued to demand Tehran suspend uranium enrichment, Iran's state broadcasting company reported.
Ali Larijani's comments came a day after the U.S. and France took Iran to task during a conference on nuclear proliferation for defying a U.N. Security Council demand that it freeze enrichment. "If the West again applies the past wordings about Iran's nuclear case, this issue will not conclude," the Web site quoted Larijani as saying. "They should abandon this idea that they can change conditions of Iran's nuclear case by applying harsh word policy." When he goes to Saudi Arabia on Saturday, Cheney faces a difficult diplomatic mission - trying to ease concerns of King Abdullah about the direction of al-Maliki's Shiite-dominated government in Iraq. Abdullah has increasingly sent signals that he doubts the U.S. troop buildup to help secure Baghdad will work. The king refused to see al-Maliki as the Iraqi prime minister was making a tour of Arab countries late last month. And during a regional conference in the Egyptian resort of Sharm el-Sheik in early May, Saudi Arabia's foreign minister was one of the few Arab diplomats al-Maliki did not meet in face-to-face talks. Abdullah's snub to al-Maliki appeared aimed at showing Saudi Arabia's concern that the Iraqi government is too close to Iran and is not doing enough to reconcile with Iraq's Sunni Arab minority, a Saudi official said at the time. Iran, like Iraq, is heavily Shiite. Saudi Arabia has a predominantly Sunni Muslim population. The visit to the Stennis was a return trip for Cheney, who came to the carrier - then in the Arabian Sea - in March 2002 as he was trying to build support in the area for invading Iraq. Cheney flew to and from the carrier Friday by helicopter. AP-CS-05-11-07 2113EDT