Air China is suspending flights between Beijing and the North Korean capital of Pyongyang.

The suspension of service by the state-owned carrier will go into effect from Monday, according to Chinese state media.

A representative for Air China said the airline was temporarily suspending flights due to weak sales.

"We will schedule flights on this route based on passenger demand," the representative told CNN.

The suspension, however, comes amid rising tensions on the Korean peninsula. North Korea, which is developing nuclear and ballistic missile capabilities, is facing increased pressure from the Trump administration to curtail work on the programs.

Air China had been operating three round-trip flights a week between the two capital cities, according to its published timetable. But service had become sporadic in recent months.

The suspension threatens to sever a key link between the isolated nation and the outside world.

The U.S. and its allies have tried for years to squeeze the North Korean government's supply of money and cut it off from the global banking system. All that seems to have done is develop Pyongyang's ability to dodge sanctions.

China is North Korea's economic bedrock, accounting for more than 80% of its smaller neighbor's foreign trade.

North Korea's biggest source of foreign currency is believed to come from the millions of tons of coal it sells to China every year. This accounted for about a third of official exports in 2015.

President Trump issued a series of tweets on Tuesday calling on China to "solve the North Korean problem."

I explained to the President of China that a trade deal with the U.S. will be far better for them if they solve the North Korean problem! — Donald J. Trump (@realDonaldTrump) April 11, 2017

North Korea responded by warning of a "merciless" response to any hostile military, economic or political moves by the "reckless" Trump administration, according to a statement from a North Korean army spokesman that appeared on the state-run news agency KCNA.

Related: Photos from inside North Korea

North Korean state carrier Air Koryo offers regular service between Pyongyang and the Chinese cities of Beijing and Shenyang.

-- Will Ripley, Jon Ostrower, Pamela Boykoff and Steven Jiang contributed reporting.