Myanmar President Invites U.S. Businesses to Return SIEM REAP, Cambodia - President Thein Sein of Myanmar invited American business executives on Friday to return to his impoverished country after an absence of 25 years, promising them an easing of economic restrictions to smooth the way. It was the latest sign of a significant warming of relations between the United States and Myanmar, a Southeast Asian country that had been firmly in China's orbit. Secretary of State Hillary Rodham Clinton welcomed Mr. Thein Sein at a dinner in this ancient Cambodian city on the last full day of her Asia trip, one intended to show that Washington's commitment to the region reached beyond strengthening of military alliances to include interest in expanding economic ties as well. Most countries in the region, with the Philippines as an exception, do more trade with China than with the United States. The meeting followed President Obama's announcement on Wednesday of the easing of sanctions on American investments in Myanmar, a decision reached after two months of debate within the administration over how much and how quickly to reward the Myanmar government for the reforms it has undertaken so far. The administration placed some conditions on investments, including the requirement that American companies investing more than $500,000 must report to Washington on their human rights policies and anticorruption efforts. American energy companies that conclude deals with the state-owned Myanmar Oil and Gas Enterprise - which the opposition leader, Daw Aung San Suu Kyi, wanted to be kept under sanctions - will be required to report their investments to Washington within 60 days. The meeting of American business executives at a hotel in the city that is a base for tourism to the hundreds of temples near here was organized weeks ago in anticipation of Mrs. Clinton's trip to Japan, Mongolia, Vietnam, Laos and Cambodia, her last stop in Asia before flying to Egypt on Saturday and then to Israel. While few chief executives of major companies made the trek to this out-of-the-way location, the audience of several hundred, many of them regional representatives of United States corporations, received Mr. Thein Sein, a former military general, warmly. Dressed in a business suit instead of the traditional Myanmar attire he wears at home, Mr. Thein Sein spoke in English about how his government was dropping the "centralized system" of the past 50 years. Antiquated laws that prevented foreign investment in the past are in the process of being removed, he said, adding that bigger challenges lay ahead. "We must also reform the bureaucratic system and the mind-set of government officials," he said. Mrs. Clinton and Mr. Thein Sein met for an hour before the dinner, and Mr. Thein Sein stressed, according to a senior State Department official, that his government wanted to attract American businesses that not only exported Myanmar's plentiful raw materials but also brought added value to the country to aid in its development. For example, the president told Mrs. Clinton, Myanmar exports teakwood, but not finished teak products. The country exports rubber but imports tires, he said. For her part, Mrs. Clinton told Mr. Thein Sein that the United States was concerned about the treatment of the Rohingya Muslim ethnic group, which has suffered killings at the hands of Buddhists, the State Department official said. The announcement of the easing of the sanctions will allow executives of nearly 50 American companies who attended the dinner, including those of FedEx, Cargill and Chevron, to leave Siem Reap on Saturday morning for a trip to Myanmar. Robert D. Hormats, the under secretary of state for economic growth, energy and environment, is heading the delegation. "It is more than a quarter of a century since a high-level United States government and business delegation went to Burma," Mr. Hormats said. Burma, the traditional name of Myanmar, is used by the State Department. The first American ambassador to Myanmar since 1990, Derek J. Mitchell, arrived this week in Yangon, the capital, and attended the dinner here with Mr. Thein Sein. Western business executives say they are aware of the opportunities in Myanmar, but that there are also big hurdles. A modern banking system does not exist, communications are spotty, and ingrained corruption linked to military officers is widespread.