Tesla (TSLA -1.11%) customers in the United States can now buy vehicles using Bitcoin (BTC -1.34%), deepening the relationship between the electric vehicle manufacturer and the cryptocurrency.

Tesla last month disclosed it had bought $1.5 billion worth of Bitcoin to augment its cash balances, saying at the time that it intended soon to accept the digital currency as payment for new vehicles. CEO Elon Musk in an early morning tweet on Wednesday said the option is now available in the U.S., with customers in other countries expected to have the choice "later this year."

Musk said that Tesla intends to keep whatever Bitcoin it receives as payment, and not convert it to fiat currency. Bitcoin climbed more than 4% after the announcement. Shares of Tesla opened down slightly on Wednesday morning.

A Tesla vehicle outside of an urban area.

Image source: Tesla.

It's unclear how many customers will take advantage of the option. Bitcoin so far has proved to be volatile but is thought of by many as a long-term investment, and not a currency. Someone who holds Bitcoin and believes it is likely to appreciate over time might not want to trade it for an automobile that will depreciate.

Musk himself has said that he sees Bitcoin as an appreciating asset, justifying Tesla's decision to convert some of its reserves to the cryptocurrency because interest rates paid on cash are currently low.