Bitcoin's price rally this year continues to attract skeptics.

The latest to join the fray is Katsunori Sago, chief investment officer of Japan Post Bank, who said he believes the world's largest cryptocurrency by market capitalization is in bubble territory.

Speaking to Reuters today, Sago argued that the true fair value for bitcoin is around $100, adding that the current high value of the cryptocurrency is worse than the dot-com bubble of the late 1990s.

Sago said if bitcoin did drop to $100, the bank might consider buying it, but due to high volatility there are no plans to short-sell the cryptocurrency. According to the news source, the CIO also predicted that the bitcoin rally could top out around $10,000 when CME Group launches its bitcoin futures product – a move expected by the end of 2017.

However, he also aired a positive sentiment on blockchain technology and predicted that, in years to come, bitcoin could come to be widely used in settlement.

"The best thing to do here is to stay away from it [until then]," he said.

Sago's take on bitcoin mirrors views of other big names in finance. Earlier today, Morgan Stanley CEO James Gorman said bitcoin's meteoric price gains are "by definition speculative."

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