Trump initially said on social media on Sunday that his January executive order on digital assets would create a stockpile of currencies including XRP (Ripple), SOL (Solana), and ADA (Cardano).
The assets rose 10 per cent to 35 per cent in trading on Sunday.
Other digital assets also gained.
Trump then added that the reserve would also include bitcoin and ethereum.
Trump said his order "directed the Presidential Working Group to move forward on a Crypto Strategic Reserve that includes XRP, SOL, and ADA. I will make sure the US is the Crypto Capital of the World."
The Republican president won support from the crypto industry in his 2024 election bid, and he has quickly moved to back their policy priorities.
Under his Democratic predecessor Joe Biden, regulators cracked down on the industry in a bid to protect people from fraud and money laundering.
In recent weeks though, cryptocurrency prices are down sharply, with some of the biggest digital currencies erasing nearly all of the gains made after Trump's election win triggered a wave of excitement across the industry.
Analysts say the market needs a reason to move higher, such as indications that the US Federal Reserve plans to cut interest rates or a clear pro-crypto regulatory framework from Trump's administration.
Trump is hosting the first White House Crypto Summit on Friday.
His family has also launched its own coins.
It is not clear how the new stockpile will be set up or work.
Analysts and legal experts are divided on whether an act of Congress will be necessary.
Some have argued the reserve could be created via the US Treasury's Exchange Stabilization Fund, which can be used to purchase or sell foreign currencies.
Trump's crypto group had planned to look at potentially creating the stockpile with cryptocurrencies seized in law enforcement actions.
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