U.S. President George Bush says Iran must unconditionally release 15 British naval personnel seized this past week. VOA White House Correspondent reports, Mr. Bush discussed the matter Saturday with Brazilian President Luiz Inacio Lula da Silva who vowed to continue his country's commercial ties with Iran.

President Bush, right, and Brazil's President Luiz Inacio Lula da Silva attend a joint news conference at Camp David, MD

Iranian President Mahmoud Ahmadinejad Saturday again said the Britons illegally entered Iranian waters and criticized Prime Minister Tony Blair's government for refusing to apologize or express regret for the situation.

Britain says its naval personnel were in Iraqi waters when they were overwhelmed by a larger force from Iran's Revolutionary Guards. Tehran says they illegally entered Iranian waters when they were picked up in the disputed Shatt al-Arab waterway between Iran and Iraq.

The standoff further raises international tensions with Iran over its enrichment of uranium. That is one of the reasons the United States is asking Brazil's national petroleum firm, Petrobras, to stop working in Iran.

Following talks with President Bush at Camp David, President Lula,speaking through a translator, said Brazil has no political differences with Iran and will not suspend commercial ties that are not in violation of a U.N. embargo. "Petrobras will continue to invest in oil prospection in Iran. Iran has been an important trade partner for Brazil. They buy from us more than one billion dollars and they don't almost sell anything to us. So I am an advocate that fair trade is the trade that you buy and sell," he said.

President Bush says he hopes nations would be very careful in dealing with Iran because, he says, the country is trying to develop a nuclear weapon that would be a major threat to world peace. Mr. Bush had little choice but to accept President Lula's decision to maintain commercial ties with Iran. "Every nation makes the decisions that they think is best for their interests. Brazil is a sovereign nation. He just articulated a sovereign decision," he said.

The United Nations Security Council has expressed "grave concern" about the detention of the British sailors, and has called for an early resolution to the standoff.