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Apple Inc. (AAPL - Get Report) led tech stocks lower Monday as investors braced for the possibility of fresh tariffs on China-made goods, including mobile phone imports, as trade talks between the world's two biggest economies look close to collapse.

President Donald Trump Tweeted Sunday that tariffs on $200 billion worth of China made goods would rise from 10% to 25% by the end of this week, and added that a similar levy on another $325 billion could be placed on China imports "shortly". Trump incorrectly claimed that China was paying tariffs to the United States, and characterized the talks, which were renewed with much fanfare in early December, had been moving "too slowly".

Apple shares were marked 1.8% lower at the start of trading Monday to change hands at $208.00 each, while shares in Microsoft (MSFT - Get Report) , which generates around 10% of its revenues in China and could be vulnerable to a retaliatory tariffs from Beijing, fell 1.23% to $127.32 each. Advanced Micro Devices (AMD - Get Report) , which gets around a third of its revenues from China, fell 4% to $27.08 each. while rival chipmakers Nvida (NVDA - Get Report)  and Micron (MU - Get Report) were seen 3.4% lower at $176.82 and 4.4% lower at $41.41 respectively.

Curiously, Trump's tariffs threat comes not only less than two days after he said talks with Beijing had been "going along pretty well," but also less than a week after Apple CEO Tim Cook said the trade dialog between the two countries had improved.

""From our point of view, this has affected consumer confidence on the ground there in a positive way," he told investors on a conference call following the tech giant's better-than-expected second quarter earnings. "And so, I think it's a set of all of these things and we certainly feel a lot better than we did 90 days ago."

If Trump were to make good on his threat, the new levels of tariffs would surpass all of the more than $540 billion of goods imported into the U.S. last year, leaving consumer tech products such as iPhones and iPads vulnerable to levies that would raise their end prices for American consumers.

The U.S. imported around $54 billion worth of mobile phones from foreign suppliers last year, according to International Trade Center data, with more than 80% of that figure coming from China. 

A recent analysis from IHS Markit estimated that the factory cost of an iPhone 7, which is assembled in China but uses components from various countries including South Korea, Japan and Taiwan, is about $237, a figure that is then used by U.S. customs officials when they are calculating trade activity with China.

However, the U.S. contribution to the construction of an iPhone is around $69, compared to the China-based contribution of around $8.50, meaning tariffs based on the import of an iPhone would hit both U.S. companies and U.S. consumers harder than they would those in China.

Last year, CEOs from some of the biggest U.S. tech companies, including Cisco Systems (CSCO - Get Report)  , Dell Technologies (DELL)  , Hewlett Packard Enterprises (HPE - Get Report)  , urged U.S. Trade Representative Robert Lighthizer to consider the "broad, disproportionate economic harm to U.S. interests, including our companies and U.S. workers, our customers, U.S. consumers, and broader U.S. economic and strategic priorities" that tech-focused tariffs would have, while slowing investment for the rollout of 5-G networks and advances in cloud computing.

"In addition to leaving us with less capital to invest in research and development, over time the reduced profits that the duties could cause could lead to hiring freezes, stagnant wages, and even job losses, as well as harm to investors such as reduced dividends and erosion of shareholder value," the companies said.