The presidents of two leading oil producing nations, Venezuela and Iran, are due to meet to discuss closer economic co-operation.
The two leaders have met several times before
Hugo Chavez and Mohammad Khatami are expected to sign a number of energy deals during President Khatami's three-day visit to Caracas.
Both countries have strained relations with Washington.
Iran denies US charges of seeking nuclear weapons, while the US has called Mr Chavez a "negative force".
Last month, Mr Chavez, a close ally of Cuban President Fidel Castro, accused the US of trying to kill him - a charge dismissed by the state department in Washington as "ridiculous and untrue".
Mr Khatami's visit will be his third to Venezuela. Mr Chavez visited his Iranian counterpart in Tehran in November last year.
Venezuela is one of the leading suppliers of petroleum to the US, but recently it has been seeking alternative energy partners such as Russia, China and India.