WASHINGTON -- Sanctions against North Korea could be tightened by cutting off its oil supply and interdicting vessels transporting goods to and from the country, a senior South Korean government official said Wednesday.

Those are the two main options that remain in the wake of North Korea's latest long-range missile launch Tuesday, the official told reporters on condition of anonymity.

"I think the US is figuring out how to let that play out," he said on a visit to Washington. "I can't tell you whether the US wants to unilaterally use maritime interdictions or include them in a new UN Security Council resolution because I think they're still thinking about it."

North Korea has come under growing sanctions for its nuclear and ballistic missile programs, including a ban on exports of iron, lead and other key sources of revenue.

Still, the communist regime has accelerated its pursuit of a nuclear-tipped missile capable of reaching the US mainland and claimed success with its test Tuesday of an intercontinental ballistic missile.

US Secretary of State Rex Tillerson issued a statement shortly after the launch that urged the international community to step up maritime interdictions of trade with the regime.

On Wednesday, US President Donald Trump vowed to impose "additional major sanctions" on Pyongyang.

But cutting off the oil supply will depend on China, which is responsible for almost all trade with the isolated nation.

At the UN, US Ambassador Nikki Haley said Trump has asked Chinese President Xi Jinping to take that crucial step. (Yonhap)