Iranian President Mahmoud Ahmadinejad and Venezuela's Hugo Chavez lavished praise on each other on Monday, mocked U.S. disapproval and joked about having an atomic bomb at their disposal.

Despite their geographical distance, the fiery anti-U.S. ideologues have forged increasingly close ties between their fellow OPEC nations in recent years, although concrete projects have often lagged behind the rhetoric.

One of the targets that Yankee imperialism has in its sights is Iran, which is why we are showing our solidarity, Chavez said during a joint press conference. When we meet, the devils go crazy, he said, mocking U.S. warnings that Latin American nations should not help the Islamic Republic.

But the two countries signed only vague cooperation accords and Chavez gave few signals that Venezuela would seek to undercut toughened sanctions over Iran's nuclear program by providing fuel or cash.

They appeared to cautiously avoid statements on sensitive issues including Iran's threat to close the Straight of Hormuz, a shipping channel crucial for the global oil trade.

Ahmadinejad was in Venezuela at the start of a tour intended to shore up support as expanded Western economic sanctions take effect over Iran's nuclear program.

The imperialist madness has been unleashed in a way that has not been seen for a long time, Chavez said in a ceremony to welcome Ahmadinejad at his presidential palace in Caracas.

The two men hugged, beamed, held hands and showered each other with praise.

President Chavez is the champion in the war on imperialism, Ahmadinejad said.

The agreements include an economic cooperation deal that offered few details and another relating to nanotechnology.

They did not include any arrangement for Venezuela to provide fuel to Iran, which in the past led Washington to impose relatively mild sanctions on the South American nation, or any economic lifeline to Iran which now faces threats to its all-vital oil income.

Venezuela's oil minister said the Organization of the Oil Exporting Countries, or OPEC, did not plan to make any statement about the sanctions.

As he often does, the theatrical and provocative Chavez stuck his finger right into the global political sore spot, joking that a bomb was ready under a grassy knoll in front of his Miraflores palace steps.

That hill will open up and a big atomic bomb will come out, he said, the two men laughing together.

U.S. officials from President Barack Obama down have expressed disquiet over Venezuela's close ties with Iran. They fear Chavez will weaken the international diplomatic front against Iran and could give Tehran an economic lifeline.

The United States and its allies accuse Iran of aiming to produce a nuclear weapon. Iran says its nuclear program is only for power generation and other peaceful purposes.

As well as Venezuela, Ahmadinejad plans to visit Nicaragua, Cuba and Ecuador - a tour that Washington has said shows its desperation for friends.

You're going to the axis of evil, Ahmadinejad, Chavez joked, referring to allied Latin American countries that have openly confronted the United States.

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Those nations' governments share Chavez's broad global views, but do not have Venezuela's economic clout and are unable to offer Iran any significant assistance.

Regional economic powerhouse Brazil, which gave the Iranian leader a warm welcome when he visited during the previous government of Luiz Inacio Lula da Silva, was notably absent from his agenda this time.

Ahmadinejad, who is subordinate to Supreme Leader Ayatollah Ali Khamenei on foreign policy and other matters, has said little about the rising tensions with the West, including the sentencing to death of an Iranian-American man for spying for the CIA. The United States denies that the man is a spy.

The only bombs we're preparing are bombs against poverty, hunger and misery, added Chavez, saying Iranian constructors have built 14,000 new homes in Venezuela recently.

Ahead of hosting Ahmadinejad, Ecuador's government also offered moral support, pledging to ignore Western sanctions.

We say with clarity that we do not accept those sanctions, Foreign Minister Ricardo Patino told reporters.

We are a sovereign nation, we don't have dads punishing us and putting us in the corner for behaving badly. They (the U.S.) should instead be sanctioning the U.S. companies doing massive business in Tehran like Coca-Cola and Pepsi-Cola.

(Additional reporting by Enrique Andres Pretel in Quito; editing by Will Dunham and Mohammad Zargham)