The US government did not aim to force the sale of TikTok but rather wanted to ban it, the owner of the short video-sharing app has said.

Mr Zhang Yiming, the founder of ByteDance which owns TikTok, said in a second letter to employees in as many days that it is prepared for further difficulties as he personally came under attack from Chinese nationalists who have accused him of being a traitor.

TikTok is in the midst of negotiating a sale to Microsoft after President Donald Trump threatened it with an outright ban in the United States, citing national security reasons, unless the company is sold to an American firm.

"The focus of the problem is not that CFIUS (Committee on Foreign Investment in the United States) forced the sale... the real purpose (of the administration) was for a comprehensive ban and more," Mr Zhang wrote in the letter addressed to the Chinese staff of ByteDance.

The company has gone to great lengths to separate TikTok's international operations from the Chinese part of the firm, which runs Douyin and Jinri Toutiao, a news aggregator that doubles as a social networking site.

In the letter, Mr Zhang referred to the personal attacks he has received on Weibo for appearing to bow to American pressure, including old posts where he spoke highly of the US system. He has now deleted all his social media posts.

"I actually understand that people have high expectations for a Chinese company going global," he wrote. "Furthermore, people have a lot of grievances now of the US government, so it is easy to criticise us very fiercely."

But offline, Beijing has leapt to TikTok's defence, accusing the US of "outright bullying" and calling its actions tantamount to theft.

"(The forced sale) goes against the principles of the market economy and the (World Trade Organisation's) principles of openness, transparency and non-discrimination," said Chinese Foreign Ministry spokesman Wang Wenbin.

"The US, without providing any evidence, has been using an abused concept of national security... unjustifiably suppressing certain non-US companies," he said.

The national security grounds for Washington's clampdown on Chinese firms "do not hold water", and Chinese companies conduct business activities in accordance with international rules and US laws, Mr Wang said.

"But the US is cracking down on them on trumped-up charges. This is all political manipulation," added Mr Wang, warning Washington not to "open Pandora's box".

"As TikTok's experience shows, no matter how unfounded the claims against them are, as long as they remain Chinese companies, they will be presented as being a 'Red threat' by the administration," the official China Daily wrote in an editorial, calling the move officially sanctioned theft.

"But China will by no means accept the 'theft' of a Chinese technology company, and it has plenty of ways to respond if the administration carries out its planned smash and grab," it added.