Taiwan said Saturday it is an "independent" nation, hours after US President Donald Trump warned the democratic island against declaring formal independence.

Trump wrapped up a state visit to Beijing on Friday where Chinese President Xi Jinping had pressed him not to support Taiwan, which China claims is part of its territory.

Taiwan depends heavily on US security backing to deter China from carrying out its threat to annex the island by force.

Taiwan "is a sovereign and independent democratic nation, and is not subordinate to the People's Republic of China", Taiwan's foreign ministry said in a statement.

The ministry also insisted that US arms sales were part of Washington's security commitment to Taiwan, after Trump said it "depends on China" and was a "very good negotiating chip for us".

Taiwan's statements came after Trump issued a warning to the island against making a declaration of independence.