United Nations Secretary-General Ban Ki-moon is on a two-day visit to California to discuss climate change and other global challenges. Mike O'Sullivan reports from San Francisco, the secretary-general says the United Nations suffers an image problem in the United States, but that the organization remains the best hope for solving international problems.

U.N. Secretary-General Ban Ki-Moon says the challenges facing the world today require dialogue and collective action. He lists the main issues, as he sees them.

"You have international terrorism, abject poverty, sanitation, pandemic diseases, and most importantly these days, climate change issues," he said.

Ban, who addressed San Francisco's World Affairs Council Thursday, said global warming will be a U.N. priority during his tenure. He says the United States, the leading emitter of greenhouse gases such as carbon dioxide, which contribute to global warming, can play a pivotal role in solving the problem.

"The United States is the largest emitter," he said. "But what is fortunate is that the United States is the biggest technological innovator."

Ban is the former South Korean foreign minister, and he has been at the helm of the United Nations for just seven months. He says the world body is under-appreciated in the United States, and he cites a poll in which two-thirds of Americans said they believe the United Nations is doing a poor job.

On a more positive note, the U.N. chief says, nearly three-quarters of Americans believed the United Nations should play a bigger role in solving the world's problems. He says he is committed to reforming the organization, increasing its efficiency and effectiveness and making its operations more transparent.

U.N. Secretary-General Ban K-moon visits with Libby Patterson

She described him as a focused and serious teenager. Today, Ban is a soft-spoken and careful diplomat, who defends his low-key manner, saying he is a man who gets things done.

"I may not offer soaring rhetoric, but I do promise results," he said.

Friday, the secretary-general will meet with a man with a more forceful style but a similar focus on environmental issues, California Governor Arnold Schwarzenegger. The two will discuss global warming and the aggressive measures California has taken to address it. Then they will visit a company that has developed technology to curb greenhouse gas emissions.