Israel, for one, is worried about the close relation between Venezuela and Iran, even warning Russia, according to The Jerusalem Post, "of the possibility that an advanced air defense system it is planning to sell to Venezuela could eventually make its way to Iran."
"The system, the S-300 – as described by the newspaper – is one of the most advanced multi-target anti-aircraft-missile systems in the world, with a reported ability to track up to 100 targets simultaneously while engaging up to 12 at the same time. It has a range of about 200 kilometers and can hit targets at altitudes of 90,000 feet".
Venezuelan President Hugo Chavez went to visit Iran on October 19th to strengthen energy, economical and political cooperation. Among the agreements signed between the two countries were pacts for the formation of a joint oil-shipping company and joint construction of petrochemical plants, as well as Venezuelan participation in the exploitation of Iran's South Pars gas field. 
Under the shipping agreement, PDV Marina, Petroleos de Venezuela SA's shipping subsidiary, and Iran's IRISL Group, plan to create a maritime oil transport firm that will enable Caracas to sell more than 500,000 bbl of crude in Europe and Asia. The two sides also reaffirmed an earlier agreement to build a refinery in Syria, Iran's main ally in the Middle East. An agreement to build the refinery was first signed in 2007 with Iran, Venezuela, and Malaysia as partners. 
During the visit, Chavez reiterated his support for Iran's nuclear program and pledged allegiance to Iranian President Ahmadinejad. The two heads of state further declared Iran and Venezuela are united in their efforts to defeat common enemies. "We will stand by Iran no matter what," said Chavez.
After Iran, Chavez visited Syria, Libya and Portugal on his 12-day tour. The US government has expressed "concern" over Venezuela's growing relations with Iran. The US Department of State stated that will monitor energy agreements between Venezuela and Iran to ensure that they do not violate international sanctions. President Obama also spoke about Venezuela's intentions to build a nuclear power plant with Russia's aid, stating, "There are international laws and we hope Venezuela will abide by them. Venezuela must act responsibly in developing nuclear energy." However, the Obama administration, apart from these declarations, did not take any strong stand in this direction.
From the Venezuelan press:
October 22, 2010
Title: "Venezuela and Iran stand together against aggression"
Correo del Orinoco (Venezuela)
Chavez: "Our solidarity is with the Islamic Revolution"
Chavez expressed his full support for Tehran immediately upon arriving in Iran […] rejecting the aggressive actions of the United States government and its attempt to destabilize the Middle East and undermine the sovereignty of Ahmadinejad's government.
On his arrival to the Middle Eastern nation, Chavez declared, "We are going to evaluate the world geopolitical situation and, above all, the tensions that imperialism continues to generate in the region, and the sanctions that have been applied to the Iranian people [by
the United Nations Security Council]. Our solidarity is with the Islamic Revolution. It is necessary to respect Iranian sovereignty."
The latest UN sanctions to which Iran has been subjected were passed in June and are the fourth such sanctions related to that country's nuclear program and its co-operation with the UN International Atomic Energy Association. Ahmadinejad has rejected the resolutions as counterproductive.
"A multipolar world to counteract the power of US imperialism"
Chavez said that the purpose of his tour, which has already included visits to Russia, Belarus and the Ukraine, from October 13 to October 18, was to highlight the importance
of a multipolar world to counteract the power of US imperialism and to create new relations between countries based on integration, cooperation and solidarity.
Chavez complained that already one newspaper in Colombia, El Colombiano, had "started something spectacular about the signing in Moscow of a deal to build the first nuclear-energy plant in Venezuela. It's the same tale, the same story of imperialism's attempt to prevent the independence of our people, and our development and industrialization".
"Ahmadinejad has supported the rights of Palestinians to a state against Israeli aggression"
Iran argues that the pressure from the United Nations Security Council is more political than grounded in any real concerns about nuclear materials. Tehran under Ahmadinejad has supported the rights of Palestinians to a state against Israeli aggression. He has also publicly supported Hezbollah against Israel. As part of the visit, Caracas and Tehran also signed more commercial accords. The two nations are building a maritime company in order to improve the efficiency of transporting petroleum.
Venezuelan ambassador to Iran, David Velasquez, explained to the press that "in this ninth visit of President Chavez to Iran we are going to deepen our industrial co-operation,
a topic which has strengthened the transfer of technology." Technological transfer of scientific, commercial, agricultural and energy know-how is critical to ensure Venezuela's long-term development and prosperity. "We are also advancing in agriculture and trade along with exchange of knowledge to continue along the road map approved by the presidents last April and May," stated Ambassador Velasquez. Regarding the visit, President Chavez also remarked, "We are building new spaces to consolidate political, cultural, scientific, technical and economic independence."
Chavez declared Venezuela's "unwavering allegiance to Iran"
[…] During a private dinner […] evening offered by President Ahmadinejad in honor of President Chavez, the two heads of states conversed amply and shared typical Iranian food. At the end of the meal, President Chavez declared Venezuela's "unwavering allegiance to Iran". "I know for a fact that Iran is not building a nuclear bomb," the Venezuelan President proclaimed to the dinner guests.
"And I also know," he said, "that if Iran were building a nuclear bomb, President Ahmadinejad would have the courage and dignity to say so to the world. But there is no bomb or plans for a bomb here. The US Empire just seeks an excuse to attack Iran because it won't bow down to its power. We will stand by Iran no matter what." President Chavez declared.
For his part, President Ahmadinejad spoke briefly: "I agree with everything President Chavez said…We are together with Venezuela forever. We will defend each other before the attacks of aggressors and our adversaries will fall, they always do eventually. Viva Venezuela!" the Iranian President exclaimed at the end of the dinner ceremony. […]