Nuclear impasses with Iran and North Korea are the dominant issues for Secretary of State Hillary Clinton on her trip to Europe and Asia, which begins with a stopover in Germany to commemorate the 20th anniversary of the Berlin Wall's fall.

Developments in both stalemates are expected in the coming days with international patience running out over Iran's refusal to come clean about its suspected nuclear program and North Korea's refusal to return to stalled disarmament talks.

As Clinton prepared to depart early Sunday for Berlin, U.S. officials said they anticipated that the U.N.'s nuclear watchdog soon would give up hope that Iran would accept a confidence-building deal under which it would ship uranium abroad for further enrichment. That would set the stage for consideration of new U.N. Security Council penalties against Tehran.

In addition, the officials said the U.S. is nearing an announcement that it will send a special envoy to North Korea in a bid to get the North to resume the negotiations, known as the six-party talks. The envoy, Stephen Bosworth, has been invited by the North Koreans, but the Obama administration has not yet accepted.

The centerpiece of Clinton's two days in Berlin will be celebrations marking the anniversary of the Nov. 9, 1989, opening of the wall, the symbolic end of the Cold War. But behind the scenes, in meetings with German and other visiting foreign officials, the Iran question looms.

The administration is seeking support for fresh penalties against Iran. In particular, the U.S. is hoping for help from Russia, which along with China, has in the past resisted and is giving mixed signals about whether it will back them if the uranium transfer proposal is rejected.

Clinton will be at events with German Chancellor Angela Merkel, Russian President Dmitry Medvedev, French President Nicolas Sarkozy and British Prime Minister Gordon Brown, all of whose countries are involved in the Iran talks. U.S. officials said Iran will be a prime topic of conversation.

"This is a pivotal moment for Iran, and we urge Iran to accept the agreement as proposed," Clinton told reporters in Washington last week after meeting with German Foreign Minister Guido Westerwelle. "We will not alter it and we will not wait forever."

The proposal would see Iran send 1.2 tons of low-enriched uranium -- around 70 percent of its stockpile -- for reprocessing in Russia in one batch by the end of the year as a way to ease concerns that the material would be used for a bomb -- something Iran denies.

France would then convert the uranium into fuel rods that would be returned to Iran for use in a reactor in Tehran that produces medical isotopes. Fuel rods cannot be further enriched into weapons-grade material.

Western officials say Iran agreed to the deal in principle, but there have been recent conflicting signals about it and senior Iranian lawmakers are demanding that the government reject it. The International Atomic Energy Agency is attempting to persuade Iran to accept the deal; Clinton and others say time is running out.

"Our patience is not unlimited," she said.

From Berlin, Clinton goes to Singapore, where she will meet Wednesday with Asia-Pacific foreign ministers for talks that will center on North Korea.

Jeffrey Bader, a senior Asia adviser to Obama said Friday that the United States is prepared to send Bosworth to North Korea for direct talks, but only if the North understands that such contact must set the stage for the scrapping of its nuclear program.

Bader said no decision has yet been made about when or how that trip would happen.

But two other U.S. officials said Saturday that an announcement may be imminent, possibly ahead of or during President Barack Obama's Asia trip, which begins Wednesday and will include stops in Japan, China and South Korea -- all key players in the six-party talks.

North Korea said last week it had reprocessed 8,000 spent nuclear fuel rods and extracted enough plutonium to bolster its atomic stockpile, raising the stakes in an apparent effort to push the U.S. into direct negotiations.

The North pulled out of the six-party talks in April in protest at international criticism of a long-range rocket launch. It then conducted its second-ever nuclear test in May and a series of ballistic missile tests.

After her meetings in Singapore, Clinton will make a brief stop in the Philippines on Thursday to show U.S. solidarity with the nation as it recovers from a series of devastating typhoons. Clinton then returns to Singapore to join Obama for the rest of his Asia trip.