Initial discussions have been revealed by Nikkei Asia, and crucially the report comes on the heels of Secretary of State Antony Blinken warning on Monday that China has accelerated its timeline for an invasion of Taiwan. "A fundamental decision [has been made] that the status quo was no longer acceptable, and that Beijing was determined to pursue reunification [with Taiwan] on a much faster timeline," Blinken had said.

Weapons deliveries to Taipei have been considerably delayed and slowed, despite the US having approved some $20 billion total in arms sales for the self-ruled island since 2017. Defense News has cited a $14 billion backlog in sales from the US.

According to Nikkei's sources:

A person with direct knowledge of the administration's internal deliberation acknowledged that initial discussions on joint U.S.-Taiwan production had begun. It is likely for U.S. defense companies to provide technology to manufacture weapons in Taiwan, or to produce them in the U.S. using Taiwan-made parts. "This is going to take some time to really shake out," said another source, adding that the process is likely to continue throughout 2023. 

President of the US-Taiwan Business Council Rupert Hammond-Chambers has described the idea of joint production as being "right at the beginning of the process."

Ironically enough, Washington's 'all-in' support for Ukraine is named as a major factor in slowing Taiwan's weapons procurement, per Nikkei: 

The rapid increase in arms provisions to Ukraine has made it difficult for the U.S. alone to meet the global demand for weaponry. In a mid-September report, Mark Cancian, senior adviser at the Center for Strategic and International Studies, noted that U.S. inventories of Stingers, a mobile air-defense system, and HIMARS, high-mobility rocket systems, were "limited."