Iranian President Mahmoud Ahmadinejad Friday vowed that Iran would stand up to growing international pressure over its nuclear program and threatened to "respond" to attacks.

"Embargoes and sanctions against Iran have had no effect," Ahmadinejad said in an interview in Quito with Mexican television network Televisa.

Open gallery view Iran's President Mahmoud Ahmadinejad waves to reporters as he departs Quito, Ecuador, Friday Jan. 13, 2012. Credit: AP

"Naturally, if the United States wants to disturb, damage and strike the Iranian people, the Iranian people also stand very strong. It will respond firmly," he said.

Ahmadinejad left Ecuador Friday to return home after a five-day tour of Latin America, which also took him to Venezuela, Nicaragua and Cuba. The trip was seen as an attempt to side-step growing international tensions and find new markets as the European Union considers an outright embargo on Iranian oil.

Over the course of his trip, Ahmadinejad has repeatedly denied suspicion that Iran aims to make a nuclear weapon, growing concern in the international community after Iran opened a second uranium enrichment site.

"We have shown the best cooperation with the international (Atomic Energy) agency," Ahmadinejad declared. "The Iranian nuclear problem is totally political. It is clear that the United States is looking for a pretext to put a brake on the progress of the Iranian people."

On Thursday, the United States imposed a new round of sanctions on firms in China, Singapore and the United Arab Emirates for doing business with Iran, turning up the heat.

The timing of the move heightened the all-out global push by Washington and the European Union to get Iran to stop enriching uranium and start cooperating with the UN nuclear watchdog, the International Atomic Energy Agency (IAEA).

U.S. Treasury Secretary Tim Geithner has been in China and Japan this week to push for more pressure. Japan has agreed to decrease Iranian crude oil imports in stages, but China was more skeptical.

The European Union is to consider an outright embargo on Iranian oil on January 23.

Iran has retaliated to the growing pressure with threats to block oil transport through the Strait of Hormuz, which carries a large part of Middle East oil to the rest of the world.

Tensions grew even more when an Iranian scientist connected to the nuclear program was killed Wednesday in a car bomb explosion in Tehran, the third scientist to have been killed since 2010. Iran charged that Israel and the United States were behind the killing.

The United States has denied complicity.

While in Latin America, Ahmadinejad met with Ecuadorian President Rafael Correa and other officials. Correa noted that he believes Iran's denial that they are developing nuclear weapons.

On Wednesday, Ahmadinejad met with Cuban President Raul Castro and with his brother, historic Cuban leader Fidel. On Tuesday, he attended the inauguration of Daniel Ortega for a further four-year mandate as Nicaraguan president, and on Monday he met with Venezuelan President Hugo Chavez.