Updated

Iranian President Mahmoud Ahmadinejad began a four-nation Latin American tour Sunday aiming to show off relationships with allies as tensions grow over Iran's nuclear program.

It is the Iranian leader's fifth visit to Venezuela. He will also travel to Nicaragua, Cuba and Ecuador.

Tensions have been rising in the Mideast as Iran has warned it could retaliate against newly tightened U.S. sanctions by blocking shipping lanes out of the Persian Gulf. A large share of the world's oil tanker traffic passes through the Strait of Hormuz.

Ahmadinejad smiled and waved but made no comments as he stepped off a plane Sunday evening at Simon Bolivar International Airport near Caracas. He was greeted by Vice President Elias Jaua and other Venezuelan officials.

The Iranian leader was scheduled to meet Monday with his longtime ally President Hugo Chavez, who was on a trip in eastern Venezuela on Sunday.

Several hours before Ahmadinejad's arrival, Chavez rebuffed calls by U.S. officials for countries to insist that Iran stop defying international efforts to assess its nuclear program.

"What the empire does is make you laugh, in its desperation to do something they won't be able to do: dominate this world," Chavez said. "We aren't a threat to anyone. We just have rights and we're sovereign."

The U.S. and its allies accuse Iran of trying to develop nuclear weapons under the cover of a civilian nuclear energy program. France has been pressing the European Union to impose additional sanctions.

Chavez and his allies in the left-leaning Bolivarian Alliance, or ALBA bloc, have backed Iran in the dispute.

Ahmadinejad and Chavez both plan to travel to Nicaragua for Tuesday's inauguration of newly re-elected President Daniel Ortega.