Medvedev's two-day visit is part of a Latin American tour that is aimed at revitalizing Cold War-era ties with left-leaning countries of the region and is also seen as an attempt to rebuff U.S. moves in former Soviet lands.
The visit of a group of Russian warships led by a nuclear-powered cruiser, which moored off the coast Wednesday, has been portrayed by Russian media as mirroring U.S. deployments in the Black Sea in support of Moscow's adversary Georgia.
Some 1,600 Russian forces traveling on four Russian ships were joining 700 Venezuelans for patrol and rescue exercises in the Caribbean Sea that are due to start on Dec. 1, officials said.
Russian officials have denied the exercises are aimed at "third countries" and Venezuela's president rejected talk of provocation Monday, describing the exercises as an exchange between "free, sovereign countries that are getting closer."
However, the flamboyant Venezuelan leader has joined forces with Medvedev and his predecessor Vladimir Putin in denouncing U.S global might and the George W. Bush administration's plans for missile defense facilities in eastern Europe.
In September, Chavez described Russian air force exercises over Venezuela as a "warning" to the U.S. "empire."
On a tour that also includes Peru, Brazil and Cuba, Medvedev has said he wants to restore "privileged relations" with Latin American countries in a fierce contest for influence. Of those, only Cuba was formally aligned with Russia prior to the Soviet collapse.
Russian officials are expected to pursue new arms deals with Venezuela following sales that have included radars, fighter jets, helicopters and tens of thousands of Kalashnikov rifles.
The U.S. and neighboring Colombia have voiced concern about the Venezuelan purchases, warning of a potential arms race and destabilization.
Venezuela's state-run energy company is also to sign a deal with five Russian oil companies to produce and refine Venezuelan oil in the Orinoco Basin, while there are also plans for a civilian nuclear power station, officials have said.
U.S. officials have played down the military significance of the Russian-Venezuelan naval exercises, while saying they will keep a close eye on them.
Some analysts have detected an element of bluff in current Russian moves in Latin America, saying the economic crisis now buffeting Russia is likely to hinder plans such as possible Russian involvement in a South American gas pipeline.
Others have criticized the timing of Russia's show of defiance as inept given the imminent arrival in office of a new U.S. leader, Barack Obama, who has attracted support from countries around the world and may prove more flexible on the missile defense issue.
The Russian leader was due to arrive in Caracas around mid-afternoon local time and to lay flowers at the grave of independence leader Simon Bolivar before being welcomed by Chavez at an official ceremony.
He was expected to visit the Russian ships currently moored off the port of La Guaira on Thursday morning before departing for Cuba for talks with the leadership of the Americas' only one-party communist nation in Havana.