The currency touched a low of $1.3060, the weakest since October 9. Against the euro it was down 0.3 percent to 87.970 pence

A EU-UK summit has failed to yield a decision on Britain's exit from the euro zone. May said there were still considerable unresolved issues with the European Union relating to a backstop Irish border arrangement, and she said the EU proposals were unacceptable.

Earlier the Irish prime minister said he had "huge difficulties" with the border proposal.