As he openly demands Japan to return 300 kilograms of weapons-grade plutonium that the US gave as part of "Atoms for Peace" for his concern for nuclear proliferation (to the delight of China for another chance to bash Japan), President Obama allows the US to sell nuclear fuel and technology to Vietnam, and allows Vietnam to enrich uranium if they want to.
Why? According to The Hill, to counter China.
It's a curious timing, as Vietnam has just postponed the construction of its first nuclear power plant (to be built by Russian companies) for six years. Vietnam's second nuclear power plant is to be built by the Japanese consortium, but there is no news of delay for that one.
The Hill (2/24/2014; emphasis is mine):
Obama OKs nuke deal with Vietnam
President Obama signed off Monday on a controversial civilian nuclear deal with Vietnam.
The cooperation agreement with the communist nation allows the U.S. to sell nuclear fuel and technology to its former foe. It aims to help guarantee Vietnams' energy independence as China asserts a more prominent role in the region.
“I have determined that the performance of the Agreement will promote, and will not constitute an unreasonable risk to, the common defense and security,” Obama wrote in a memo for the secretaries of State and Energy.
The deal aims to get Vietnam to import the fuel it needs for its reactors instead of producing it domestically. But it doesn't bar the country from conducting its own uranium enrichment, raising concerns about nuclear proliferation.
The agreement is also seen as a potential complicating factor in the ongoing nuclear talks with Iran. Iran has repeatedly accused nuclear powers, and the United States in particular, of a double standard in terms of which nations are allowed to run nuclear programs that are allegedly for civilian purposes only.