Susan Rice says President Obama will visit the Asia-Pacific region in April. (NICHOLAS KAMM/AFP/Getty Images)

National security adviser Susan E. Rice on Wednesday laid out an ambitious agenda for the Obama administration in the Asia-Pacific region, hoping to quell doubts among allies and rivals about whether the United States will live up to its commitments after the president canceled a trip to the region last month.

In a wide-ranging address at Georgetown University, Rice announced that Obama will visit Asia in April, although she did not specify which countries. She also noted that Vice President Biden will travel to Japan, China and South Korea next month.

“The United States of America will be there — reliable, constant, strong and steady — for the long term,” Rice said in her 45-minute speech before students and foreign policy experts.

The speech, which administration officials hastily put together in the past several days, is a response to increasing criticism among U.S. allies in Asia that the Obama administration’s self-described “pivot” to the region has been more talk than action. Obama canceled his trip to a pair of economic and security summits in southeast Asia last month to remain in Washington during the partial shutdown of the federal government. Analysts said his absence severely set back progress on final negotiations on the Trans-Pacific Partnership between the United States and 11 other countries that has been a hallmark of the administration’s agenda.

Secretary of State John F. Kerry, who stood in for the president at the summits, has been focused primarily on a series of crises in the Middle East, including Syria’s chemical weapons attacks, Iran’s nuclear weapons ambitions and peace talks between Israelis and Palestinians.

But Rice said the United States remains committed to reorienting its foreign policy to focus on the fast-growing Asia-Pacific region, and she touched on the issues of national security, trade, the environment and human rights.

She also aimed a warning shot at North Korea, emphasizing that Kim Jong Un’s regime has a choice between negotiating in good faith over its nuclear weapons and missile programs or facing continued isolation and crippling economic sanctions.

“Pyongyang’s attempt to engage in a dialogue while keeping critical elements of its program running is not acceptable and will not succeed,” Rice said. “We will do what’s necessary to defend ourselves and our allies against any threat by North Korea.”

Much of her address, however, was focused on China, with which the Obama administration has tried to foster closer ties since Xi Jinping took power this year. Obama hosted the Chinese president in a summit at the Sunnylands retreat in California in June. The two agreed to pursue a “new model of major-power relations,” which analysts said has yet to be fleshed out.

Rice encouraged the Chinese Communist Party to make good on its recent blueprint for economic reforms, which she suggested “could go a long way towards leveling the playing field for private and foreign investors and moving China’s economy towards market principles. That is an opportunity we must seize.”

But she reiterated the Obama administration’s long-standing criticism of China for not doing more to stem the theft of intellectual property rights among businesses and cybersecurity violations by state-sponsored entities.

“Cyber-enabled economic espionage hurts China, as well as the United States, because American businesses are increasingly concerned about the costs of doing business in China,” she said. “If meaningful action is not taken now, this behavior will undermine the economic relationship that benefits both our nations.”

Earlier Wednesday, U.S. Ambassador to China Gary Locke announced that he would be stepping down from the post early next year.