Both are touring the energy-rich region and landing days apart in the wealthy United Arab Emirates, where the government was said to be carefully choreographing their arrivals and departures.
Cheney was expected to fly from Iraq to the Emirates capital Abu Dhabi on Thursday. Ahmadinejad, who is expected to be greeted with great fanfare as the first ever Iranian head of state to visit, is expected Sunday, after spending two days in neighboring Oman.
The Gulf Arab countries are longtime U.S. allies, but the Bush administration's unpopular war in Iraq has triggered a strong effort by Iran to woo them out of the American camp.
But for its part, Iran has many across the region scared over its insistence on developing a nuclear program which can be used for nuclear arms making.
Washington has countered Iran's growing assertiveness in the region with a flurry of diplomatic visits and sent a second U.S. aircraft carrier steaming off Iran's coast.
Leaders in the Gulf, now in the midst of a lucrative economic boom, fear being sandwiched in a disastrous U.S.-Iran war. Neither Cheney nor Ahmadinejad is expected to win big concessions from the Gulf Arabs.
"We have a deep mistrust of both sides," said Mustafa Alani of the Dubai-based Gulf Research Center. "Each is trying to defend his corner on major issues in the region. But neither is likely to accomplish very much."
Cheney, who is also traveling to Saudi Arabia, Egypt and Jordan, is expected to press Emirates president Sheik Khalifa bin Zayed Al Nahyan for support for U.S. efforts in Iraq, and to shut down Iranian companies here that U.S. officials believe are backing the country's nuclear development. Some 500,000 Iranians live in the Emirates, which lies just across the Persian Gulf from Iran.
"We have a common interest with the U.S. in preventing Iran from becoming a nuclear power and intervening in Iraq and Lebanon," Alani said. "But the problem is that we have a huge mistrust of the U.S. and cannot publicly support its position."
Ahmadinejad wants the Emirates, Oman and the other Gulf Arab countries to drop their military alliances with Washington and join Iran in a regional effort to maintain stability in the energy-rich Gulf. Washington maintains 40,000 troops on land bases in Gulf countries outside Iraq and currently has 20,000 sailors and Marines in the region.
"Iran is maintaining the policy of persuading the Gulf states from being allied with America," said Sadeq Zibakalam, a Tehran University political scientist. "Perhaps Ahmadinejad as a hardline president will also be assuring his hosts that there is no need to be afraid of us."
Ahmadinejad is responding to an invitation to visit the Emirates, the first time an Iranian leader will have made the trip since the six sheikdoms banded together as a nation in 1971.
No Gulf state has backed Iran's offer of an alliance. Instead, Gulf leaders' agenda with Iran looks closer to America's, Alani said. Sheik Khalifa and Oman's Sultan Qaboos bin Said are likely to press Ahmadinejad to make concessions on its nuclear dispute with the West and give assurances that it is not aimed at producing weapons.
The two Gulf leaders may also warn Iran to stop backing Shiite Muslim radicals in Iraq and Lebanon, officials said. Ahmadinejad heard similar entreaties during his March visit with Saudi King Abdullah.
But the Emirates made a conciliatory move ahead of the Iranian president's arrival, announcing Wednesday that it would release 12 Iranian divers captured this month in disputed Gulf waters.
An Emirates government official, speaking on condition of anonymity because he was not authorized to talk on the record, said leaders here will press Ahmadinejad to resolve the status of three disputed Gulf islands. If Iran, which administers the islands, agrees to allow an international arbitrator to decide their status, the two countries could embark on much closer relations, analysts say.
"Together Iran and the Gulf states can take care of the region's security," said Zibakalam, the Tehran professor. "If there are problems, like these islands, they could be solved with good will and cooperation."