WASHINGTON - Moving to encourage reform in Myanmar ahead of a landmark trip by President Barack Obama, the United States has scrapped a nearly decade-old ban on most imports from the long-isolated nation.

The world’s largest economy will open up to products from the country formerly known as Burma with the exception of gems, a sector seen as a major driver of corruption and violence. The gesture is “intended to support the Burmese government’s ongoing reform efforts and to encourage further change, as well as to offer new opportunities for Burmese and American businesses,” a statement from the State and Treasury departments said.

The statement said Myanmar’s government and opposition icon Aung San Suu Kyi both supported the step to “further integrate their country into the global economy.” Secretary of State Hillary Clinton had pledged to normalize trade relations with Myanmar when she met in September in New York with President Thein Sein, who has startled critics by launching a wave of democratic reforms.

Obama on Monday will become the first sitting US president to visit Myanmar, making a trip that just years ago would have been considered unthinkable. Aides said Obama would encourage further change in the nation historically in China’s orbit. The administration’s statement said that despite the “positive changes,” the United States remained concerned about continued political prisoners, ethnic conflict, corruption and Myanmar’s lingering military ties to North Korea.

The administration issued a waiver on the import ban, which was imposed by Congress in 2003, and the law remains in place if officials decide to resume the sanctions.

The US move could bring major growth to Myanmar’s garment industry, as the United States was once the main buyer of clothes made in the low-cost nation. Total US imports from Myanmar hit a high of $470 million in 2001.

Alongside the announcement on imports, the Treasury Department added seven names to a blacklist of Myanmar firms with which US companies are barred from doing business.

The companies, four of which have addresses in Singapore, are considered front companies by two “cronies of the former regime,” the Treasury Department said. Myanmar nominally ended nearly half a century of military rule last year. Thein Sein, a former general, has since freed political prisoners, reached out to ethnic rebels and eased censorship.

Some human rights groups have accused Obama of moving too quickly, saying that he could use the prospect of a trip or the easing of sanctions as incentives for further steps such as ensuring free elections.

But US lawmakers have largely supported Obama as he has taken steps with the blessing of Suu Kyi, who has entered parliament after nearly two decades under house arrest. Suu Kyi enjoyed a hero’s welcome when she visited Washington in September.

Representative Joe Crowley of New York, a longtime champion of sanctions bills on Myanmar, said he agreed with Suu Kyi in supporting the waiver.

“The ball is now clearly in the Burmese regime’s court and we call on them to respond with concrete action, by expeditiously releasing all remaining political prisoners, putting a firm end to ethnic violence and implementing constitutional reform,” said Crowley, a member of Obama’s Democratic Party.