Americans are being blocked from downloading WeChat and TikTok.

US President Donald Trump has declared TikTok a “national emergency”, and banned any “transactions” with the Chinese owners of the apps.

The bans mean both TikTok and WeChat will no longer be distributed in US app stores, nor will any updates.

The apps are known for the large amounts of data they harvest, and concerns the Chinese Government will demand access to it.

Mr Trump has alleged that TikTok can run disinformation campaigns to benefit the Chinese Communist Party (CCP).

WeChat's 19 million daily active users in US may notice the app beginning to degrade from Sunday, due to compatibility issues and a lack of upgrades.

The US has also barred data hosting within the United States for WeChat, content delivery services and networks.

“It may still be usable but it is not going to be as functional as it was,” an official told reporters.

Tencent, which owns WeChat, says it will continue talking with the Government and other US stakeholders.

“WeChat was designed to serve international users outside of mainland China and has always incorporated the highest standards of user privacy and data security,” the company said.

Meanwhile, over 100 million existing Tiktok users in the US can continue enjoying the app until mid November, when a ban on some technical transactions will affect functionality.

In Australia, reports say the Federal Government is running investigations into TikTok, while Home Affairs is scrutinising WeChat.

Prime Minister Scott Morrison says the Federal Government will not ban TikTok, but he has warned that the app “connects right back to China”.

“There's nothing at this point that would suggest to us that security interests are being compromised, or Australian citizens are being compromised,” Mr Morrison said earlier this year.

“We'll obviously keep watching them, but there's no evidence to suggest to us today that [a ban] is a step that is necessary.”