SEOUL • United States President Donald Trump and his South Korean counterpart have pledged "stronger pressure" on Pyongyang, Seoul said yesterday after North Korea defied tough new sanctions with a missile test and said it wanted to match American nuclear strength.

The international community is scrambling to contain an increasingly belligerent North Korea, which in recent weeks has prompted global alarm by conducting its sixth and largest nuclear test and firing long-range missiles over Japan that it says could reach the US mainland.

In a phone conversation yesterday, South Korean President Moon Jae In and Mr Trump "gravely condemned" the latest missile test last Friday, which came just days after the United Nations Security Council announced a raft of new sanctions against Pyongyang.

"The two leaders agreed on more practical and stronger pressure... to make the North Korean regime realise that further provocation will only bring stronger diplomatic isolation and economic pressure, leading to a path of collapse," South Korea's presidential office said in a statement.

Pyongyang says it needs nuclear weapons to protect itself from "hostile" US forces and is determined to build a weapons system capable of delivering a nuclear warhead to strike the US mainland.

North Korean leader Kim Jong Un, who oversaw the latest missile test, said the launch was part of the country's plan to achieve "equilibrium of real force" with the US.

Experts believe Pyongyang's weapons programme has made rapid progress under Mr Kim, with previous sanctions having done little to deter it.

The UN Security Council, which has condemned last Friday's launch as "highly provocative", will hold a ministerial-level meeting on Thursday on the proliferation of weapons of mass destruction, focused on enforcing sanctions on Mr Kim's regime, diplomats said.

The meeting will be held during the annual General Assembly gathering of world leaders, where Mr Trump will meet the leaders of Japan and South Korea on the sidelines to address the crisis.

Last week, the UN Security Council imposed the strongest set of sanctions against North Korea, slapping an export ban on textiles, freezing work permits to North Korean guest workers and placing a cap on oil supplies.

China has opposed the US' demand for an oil embargo on North Korea for fear of triggering a collapse in the impoverished state. But some experts say Beijing may be resisting a total ban due to a practical reason: The oil that flows in the Dandong-Sinuiju pipeline contains a high proportion of wax.

"If production is halted, the pipes will clog up," wrote energy information company Rim Intelligence in a report released last year.

"If the wax ingredient hardens, reopening the pipes will require heating them," said Mr Takayuki Nogami, chief economist at Japan Oil, Gas and Metals National Corp.

China may fear it will not easily recover these pipelines if it stops sending oil through them, reported Nikkei Asian Review.

Oil from China's Daqing city is transported from Dandong to North Korea via underground pipes, making it hard to verify whether export restrictions are being kept.

AGENCE FRANCE-PRESSE