Iranian President Mahmoud Ahmadinejad headed for home on Friday after achieving his goal of securing the backing of four Latin American allies in his country's nuclear standoff with the West.

The Iranian leader left Quito aboard an Ecuadoran Air Force plane bound for the southwestern city of Guayaquil from where he was to fly back to his native soil.

In Quito, he defiantly vowed to resist escalating Western pressure to stop his country's alleged efforts to develop atomic weapons.

"They (the West) have decided to step up their pressure on us. They insult our country and our people. It's clear that the Iranian people will resist," he told reporters.

"The international community knows that hegemonic (Western) powers do not support the progress of independent peoples. The Iran problem is not the nuclear program, the Iran problem is the progress and independence," he added.

Washington has been leading a campaign to bring Tehran's economy to its knees by slapping sanctions on its oil exports, a crucial source of income.

President Barack Obama last month signed a law targeting Iran's central bank, which clears most of the oil payments, and US envoys have been fanning out in recent days to convince other nations to come on board or risk seeing their firms barred from doing business in America.

The UN Security Council has already approved four rounds of sanctions on Iran for refusing to halt uranium enrichment.

Ahmadinejad's five-day tour was conceived to shore up his support in Venezuela, Nicaragua, Cuba and Ecuador.

All four countries have frosty ties with the United States, and their leaders have in the past four years made numerous Tehran visits to build up diplomatic and business links while relations with Washington have worsened.

Ahmadinejad's trip, however, was overshadowed by Wednesday's killing of an Iranian nuclear scientist, which Tehran blamed on Israeli and US intelligence.

Mostafa Ahmadi Roshan, a deputy director of Iran's main uranium enrichment plant, was given a funeral service in north Tehran after noon prayers Friday.

Iran's supreme leader, Ayatollah Ali Khamenei, said the "abominable" and "cowardly" killing was committed "with the planning or support of the intelligence services of the CIA and Mossad" of the United States and Israel.

And he vowed that Tehran would "continue with determination" its nuclear activities, which Western governments suspect mask a drive for atomic weapons capability despite repeated denials.

Iran, however, said Thursday it stood ready to resume talks on its suspect nuclear activities with the five permanent members of the UN Security Council, plus Germany.

And diplomats in Vienna said the UN nuclear watchdog IAEA was to send its chief inspector and deputy director to Iran for a week from January 28 to discuss the country's nuclear activities.

Although the United States last week warned Latin American states against deepening their ties with Iran, Ahmadinejad won support from the presidents of Venezuela, Nicaragua, Cuba and Ecuador to peacefully develop nuclear energy.

Ecuadoran President Rafael Correa, who met for five hours with Ahmadinejad Thursday, denounced a recent IAEA report that found "credible" evidence that Iran had engaged in activity relevant to developing a nuclear explosive device.

"How can we accept these kinds of reports?" Correa said. "The report concluded, in quotes, that Iran was developing nuclear weapons, something it has always denied, and we believe them."

Ecuador was one of only two countries on the Vienna-based IAEA's 32-member board of governors to vote against a subsequent resolution condemning Iran's nuclear activity. The other country was Cuba.

"Iran can count on the total support of Ecuador so that the truth is known and not just the propaganda of countries which show a shameful double standard," Correa said.

During his stop in Cuba, Ahmadinejad met with President Raul Castro as well as with his 85-year-old brother and revolutionary icon Fidel Castro.

A joint statement issued by Raul Castro and Ahmadinejad highlighted the "right of all nations to the peaceful use of nuclear energy," in an implicit swipe at the Western pressure on Iran.

The Iranian leader earlier visited Venezuela and Nicaragua.