June 26 (Bloomberg) -- President Barack Obama and German Chancellor Angela Merkel called on Iran’s government to halt the violent crackdown on demonstrators and said the Persian Gulf nation must be blocked from gaining a nuclear weapon.

Obama, speaking at a joint news conference with Merkel at the White House, called the Iranian government’s response to protests over the June 12 presidential elections “outrageous.”

“A government that treats its own citizens with that kind of ruthlessness and violence and that cannot deal with peaceful protesters who are trying to have their voices heard in an equally peaceful way I think has moved outside of universal norms,” Obama said.

Merkel said the Iranian people have a right “to have their votes be counted” and to see that the election results are substantiated.

Both leaders said Iran must not be allowed to develop a nuclear weapon and that there will continue to be attempts to engage the government in Tehran on that issue. Obama repeated his warning that a nuclear weapon in Iran would trigger an arms race in the Middle East that would destabilize the region.

Merkel said the Iranian nuclear program “must be stopped.”

Diplomatic Pressure

Both leaders said the U.S. and Europe along with Russia and China must continue pressing to bring Iran into negotiations to halt its effort to enrich uranium.

“There is no doubt that any direct dialogue or diplomacy with Iran is going to be affected by the events of the last several weeks,” Obama said. He said the U.S. and other nations can’t assume there will be a “huge shift” in Iran’s stance in international relations as a result of the protests.

Obama dismissed a demand from Iranian President Mahmoud Ahmadinejad, whose re-election sparked the protests, for an apology for “interfering” in Iran.

“I don’t take Mr. Ahmadinejad’s statements seriously about apologies, particularly given the fact that the United States has gone out of its way not to interfere with the election process in Iran,” Obama said.

On another topic of discussion between the two leaders, Merkel said she welcomed action in the U.S. to address climate change. The U.S. House of Representatives is debating legislation limiting greenhouse-gas emissions and a vote may come later today.

‘Sea Change’ on Climate

“This is indeed a sea change that I see” in the U.S. regarding climate change, Merkel said. “This really points to the fact that the United States is very serious on climate.”

Obama said the legislation marks “enormous progress” from the U.S. stance under his predecessor, former President George W. Bush. He said there is still more to do, and industrial nations must bring developing nations into the discussions.

The legislation is aimed at curbing greenhouse-gas pollution from power plants, factories and other sources that a United Nations panel of scientists say likely is contributing to higher temperatures and rising sea levels.

The two leaders also touched on attempts by the U.S. to get other nations to accept detainees held at the prison camp at Guantanamo Bay, Cuba, which Obama has vowed to close by January.

“We are going to be looking for the help” from Europe in taking detainees from Guantanamo, Obama said.

Detainees

The European Union has long argued for the prison’s closure and has agreed to accept some prisoners, though it’s up to individual EU members to decide. The State Department has had trouble persuading other countries to accept some of the more than 200 prisoners.

“There have been no particular requests made about X number of detainees being placed by such and such a date,” Obama said. He said Merkel “has not made commitments,” though the chancellor said that “we are not going to shirk that particular responsibility,” once legal issues are sorted out.

Portugal said this month it would take two or three Guantanamo detainees, its foreign minister said June 21. Italy earlier this month said it would take at least three, according to an aide to Italian Premier Silvio Berlusconi. The U.S. has asked Spain to accept four prisoners. The U.S. on June 11 sent four Chinese Uighurs to the British Atlantic island of Bermuda.

Obama and Merkel, looking ahead to the G-8 summit in Italy next month, both pledged they would avoid protectionism and maintain a course of government actions leading to “sustainable growth,” Obama said.

Merkel said the summit of industrialized nations would “take stock” of new financial regulations imposed on both sides of the Atlantic that she said are meant to prevent “a future crisis” and global meltdown.

To contact the reporters on this story: Roger Runningen in Washington at rrunningen@bloomberg.net; Kate Andersen in Washington at kandersen7@bloomberg.net.

Last Updated: June 26, 2009 14:36 EDT