The suspension of flights to slow the spread of a deadly new virus is having a major impact on global flows of letters and parcels, say postal operators in the United States, China and elsewhere.

In a note seen by The Associated Press, the U.S. Postal Service informed its counterparts around the world on Tuesday that it is "experiencing significant difficulties" in dispatching letters, parcels and express mail to China, including Hong Kong and Macau, "because most of its supplier airlines have suspended their flights" to those destinations.

As a consequence and "starting immediately," USPS said it can no longer accept items destined for China, Hong Kong and Macao "until sufficient transport capacity becomes available."

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Likewise, in another, separate note seen by the AP, Singapore Post told its global counterparts that it is no longer accepting letters, parcels and express mail items destined for China, "until sufficient transport capacity becomes available."

The notes were shared with postal services around the world via the Universal Postal Union, a U.N. agency headquartered in Switzerland that is a main forum for postal cooperation between its 192 member countries.

In a statement to the AP, the UPU said that the suspension of flights because of the virus "is going to impact the delivery of mail for the foreseeable future."

"But it is hopefully temporary. The Universal Postal Union is carefully monitoring the operational situation, and is in constant contact with postal operators to ensure any backlog is cleared in the shortest possible time," it said.

The Chinese mail service, China Post, said it is disinfecting postal offices, processing centers, and vehicles to ensure the virus doesn't travel via the mail and to protect postal staff.

The virus does "not survive for long on objects. It is therefore safe to receive postal items from China," said a China Post noted transmitted via the UPU.

Letters, parcels and express mail that do still make it to China will be delivered "via non-face-to-face methods," the note said.

It said the crisis is also impacting mail that transits China to other destinations. The affected countries include North Korea, Kazakhstan, Kyrgyzstan, Mongolia, Tajikistan, Turkmenistan, Uzbekistan and Vietnam.

The note said China Post will temporarily store undelivered transit mail "and will transport it to the destination countries when these transport options are once again available."

"Delays should be expected in transport and delivery during this period," it said.

Other countries have also reported virus-related postal disruptions.

South Africa's postal service has warned of delays in receiving letters or parcels from China because of flight suspensions. In Austria, the APA news agency says the Austrian postal service is no longer sending letters or packages to China but that Austrians can still receive mail from China. In Sweden, PostNord also says letters can no longer be sent from there to China.