China on Friday issued a statement calling on all UN member states to "actively fulfill their financial obligations to the United Nations," stressing that Washington owes the organization more than $2 billion.

"As of May 14, the total unpaid assessments under the UN regular budget and peacekeeping budget amount to 1.63 billion and 2.14 billion US dollars respectively," the Chinese statement said, citing a report from the UN Secretary-General's office.

The US is the biggest contributor to the UN budget, paying 22 percent of its annual running costs, a bill which adds up to around $3 billion; and 25 percent of its peacekeeping operations, which amount to some $6 billion a year.

China pays around 12 percent of the UN's running costs and around 15 percent of the peacekeeping budget.