Bitcoin is flirting with a break below $2,500 a coin. The cryptocurrency trades down 3.7% at $2,510 and is threatening its lowest close since June 27. It's rival, ethereum is also under pressure, down 8% at $244.

Friday's slide comes amid a relatively quiet week for bitcoin. It's price has been locked in a range between $2,474 and $2,639 since Monday. That's the day when