The Obama administration has announced a $1.83bn (£1.22bn) arms sale to Taiwan in a deal that has antagonised China.
The US said the deal was consistent with its "long-standing policy on arms sales to Taiwan".
But China has said it is strongly opposed to the sale, and has pledged to sanction the US firms involved in it.
The deal, the first in four years, comes as US-China relations fray over China's construction of artificial islands in the South China sea.
Two decommissioned US Navy frigates, anti-tank missiles, amphibious assault vehicles, as well as surface-to-air missiles and other equipment are all included in the deal.
The deal will be approved in 30 days, unless Congress objects. But this is thought unlikely as there has been growing concern by Democrats and Republicans about Taiwan's ability to defend itself from China's growing military might.
State Department spokesman John Kirby said sale was consistent with the 1979 Taiwan Relations Act, which requires the US to provide Taiwan with sufficient weaponry to defend itself, even though the US does not recognise Taiwan as a state independent of China.
"There's no need for it to have any derogatory effect on our relationship with China," he told reporters. "We still want to work to establish a better, more transparent, more effective relationship with China in the region and we're going to continue to work at that."
But China summoned the US charge d'affaires in Beijing to protest against the sale.
"Taiwan is an inalienable part of China's territory. China strongly opposes the US arms sale to Taiwan," Vice Foreign Minister Zheng Zeguang was quoted by Xinhua news agency as saying.
China views Taiwan as a breakaway province which will one day be reunited with the mainland, but relations have warmed in recent weeks. Leaders from both countries met last month for the first time since the end of the civil war in 1949.
Previous US sales to Taiwan have totalled over $12bn, according to the White House.
Senate Armed Services Committee Chairman John McCain called for "a more regularised process" for selling weapons to Taiwan, saying it was needed "in order to avoid extended periods in which a fear of upsetting the US-China relationship may harm Taiwan's defend capabilities".
Tensions have risen between China and the US in recent months amid concerns from Washington that Beijing is building man-made islands in the South China Sea; the US believes that China is using the islands to expand its maritime territorial claims.
In October, the USS Lassen sailed in the Spratly archipelago as a challenge to China's claim over the islands.