Bitcoin is close to breaching a key support level that could trigger another 15% slide

• Bitcoin's 16% sell-off this month is testing a key support level at around $60,000.
• This support level is bolstered by Bitcoin's 200-day moving average of just under $58,000.

The steady decline in bitcoin this month has the cryptocurrency testing a key support level that could ultimately give way to a more painful sell-off.

Bitcoin dropped 4% on Monday and is down 16% since its June 7 high of nearly $72,000, hitting an intra-day low of about $60,000 on Monday.

According to Fairlead Strategies founder Katie Stockton, $60,000 represents a key line in the sand that should act as support for the price of the world's biggest cryptocurrency.

But if it doesn't, and bitcoin decisively breaks below $60,000, that suggests the token could continue its descent to its next support level at around $51,500.

"Support is now bolstered by the 200-day MA, giving it more significance," Stockton said in a note to clients on Monday.

Bitcoin's rising 200-day moving average is at just under $58,000.

"There are no 'Buy' signals, so we would await support discovery in bitcoin. Should a breakdown occur, it would put next support near $51,500," Stockton said.

A further decline to $51,500 would represent potential downside of about 15% from current levels, and it would represent a decline of 30% from its record-high of nearly $74,000 reached in March.

The latest sell-off in bitcoin has also rang alarm bells for the broader stock market, according to one Wall Street analyst.

"Recently the weakening of bitcoin signals an imminent S&P 500 summer correction and consolidation phase," Stifel strategist Barry Bannister said last week.