GBP/USD has embarked on a phase of pullback after facing stiff resistance near the upper limit of a multi-month channel near 1.3180. It is now challenging the lower band of this channel and is close to late June low of 1.2600/1.2570 which is a crucial support. 

An initial bounce is expected however last week's high of 1.2870 must be overcome to affirm a larger up-move. 

Failure to defend 1.2600/1.2570 could mean risk of a deeper drop; next potential supports could be at 1.2480 and 200-DMA at 1.2300.