* Graphic: sterling and gilt yields bit.ly/2dgAXn1
* Graphic: World FX rates in 2017 tmsnrt.rs/2egbfVh
* Graphic: Trade-weighted sterling since Brexit vote tmsnrt.rs/2hwV9Hv
LONDON, Dec 22 (Reuters) - Sterling weakened slightly on Friday ahead of revised economic growth numbers for the third quarter and data on the size of Britain’s current account, with traders avoiding big positions before the holiday period.
The prospect of further protracted negotiations to seal Britain’s exit from the European Union next year has weighed on the currency in December, although the pound is still up in the last two months after gaining 4 percent in November.
Analysts at Barclays said they expected the GDP number for July to September quarter to come in unrevised at 0.4 percent, in line with the consensus. The current account is forecast to narrow slightly when the data is released at 0930 GMT.
The pound was 0.1 percent weaker against the dollar at $1.336, while it was flat against the euro after retracing earlier falls at 88.67 pence per euro.
Some traders believe the pound will rally in 2018 if Britain agrees a Brexit transition deal and talks with the European Union progress faster than expected.
“The pound has been down on its luck amid a tough post-Brexit referendum backdrop. But the year ahead should see GBP bulls holding onto what they’ve got – especially now that we’re technically ‘halfway there’ when it comes to resolving Brexit,” ING said in a note. (Reporting by Tommy Wilkes; Editing by Edmund Blair)