Vatican City - The new U.S. ambassador to the Holy See urged the Vatican on Saturday to promote the potential of biotech crops, saying there was a "moral imperative" to investigate the possible benefits of agricultural technology to feed the world's hungry.

"Nothing on its own can solve the complex problem of world hunger," Ambassador Francis Rooney told Pope Benedict XVI as he presented his credentials during a Vatican audience. "But we cannot let irrational fears stop us from investigating what could be one part of the answer."

Benedict, for his part, urged the United States to continue its "generous" aid to poor countries, lamenting the "crushing debt" that can fuel poverty.

"I am confident that your nation will continue to demonstrate a leadership based on unwavering commitment to the values of freedom, integrity and self-determination," he said in remarks provided by the Vatican.

He also told Rooney that all political decisions must be based on ethical considerations that promote "the dignity, life and freedom of each human person."

The United States, home to major multinational biotech companies, has for several years touted the potential of genetically modified food to feed the world's hungry.

Critics of the technology say there is enough food to feed the world and that what is necessary is the political will and appropriate policies to fight hunger. They also warn the potential dangers of genetically modified food outweigh any benefits.

While much of Europe has been skeptical or opposed to biotech crops, Washington has found a welcome ear in some Vatican circles. The Roman Catholic Church has no specific position on the matter.

Cardinal Renato Martino, who heads the Vatican's Pontifical Council for Justice and Peace, has spoken favorably about the technology and hosted an international conference on it two years ago.

Last September, he told a conference that the Vatican was open to experimentation in the field of biotechnology, but he stressed it must be done with prudence.

In his comments Saturday, Rooney said Washington was committed to providing aid to feed the world's hungry. But he said the advance of agricultural science could help people in "even the most difficult environments" produce crops to feed themselves.

"We look to the Holy See to help the world recognize the moral imperative of a true investigation of these technologies," he said.

In his first audience with the pope, Rooney also said the United States considered the Vatican a partner in spreading peace and fighting religiously inspired terrorism.

Rooney, a Florida businessman and major Republican fund-raiser, was tapped by President Bush in July to be ambassador, replacing Jim Nicholson.