U.S. President Barack Obama says it is only a “matter of time” before Libyan leader Moammar Gadhafi gives up power.

Mr. Obama spoke Tuesday at the White House, alongside German Chancellor Angela Merkel. The U.S. president said the NATO-led mission in Libya has made “significant” progress, protecting the people from a “potential slaughter” by Mr. Gadhafi's forces.

Chancellor Merkel said Germany is “of one heart” with its NATO allies in supporting the operation in Libya. But she acknowledged that the U.S. and Germany may sometimes have differences of opinion.

Germany has kept its troops out of the operation, but President Obama said Germany has allowed other NATO allies to increase their support for the Libya mission by increasing its resources and personnel in Afghanistan.

Mr. Obama honored Ms. Merkel with the pomp and ceremony of a state visit, including a formal state dinner at the White House Tuesday evening. During the dinner, the president presented the chancellor with the U.S. Medal of Freedom, the country's highest civilian honor, one rarely given to non-Americans.

First Lady Michelle Obama said Tuesday the honor was a testament to the “extraordinary life” of the chancellor, the first woman to hold the post, as well as the first East German.

Speaking at the welcoming ceremony earlier in the day, President Obama called Germany one of the United States' strongest allies and Chancellor Merkel one of his “closest global partners.” Ms. Merkel said the United States and Germany share the same values, which she said are “democracy and freedom, rule of law and the universality of human rights.”

At their meeting, the two leaders discussed economic policy, Afghanistan and the Middle East peace process.

President Obama said they agreed that Iran's nuclear program remains a very serious concern, and that the country faces the threat of additional international sanctions if it continues to ignore its international obligations.

Mr. Obama said he and the chancellor also agreed that Europe's debt crisis must be contained. President Obama said a Greek default on its debt would be “disastrous.”

Mr. Obama said they also discussed their support for political and economic reform across the Middle East and North Africa, especially in Tunisia and Egypt. He said they agreed this historic moment “must not be squandered.”