UK's FTSE extends rally for second week on back of U.S. strength

* FTSE 100 gains 0.6 percent

* Longest winning streak for index since October

* Index just 1.5 percent off of 2013 high

By Alistair Smout

LONDON, Dec 27 (Reuters) - Britain's top share index rose onFriday, taking its cue from fresh all-time highs hit on WallStreet to notch up its sixth straight day of gains, its longestwinning streak in two months.

The gains confirmed a second straight positive week for FTSE100 returns, and a 4.6 percent rally over the lastfortnight has taken the index into positive territory forDecember.

The FTSE 100 was up 42.85 points, or 0.6 percent, at6,737.02 points by 1516 GMT, after both the Dow Jones andthe S&P 500 scaled record highs on Thursday, when the UKmarket was shut for the Boxing Day holiday.

The rise made it the UK benchmark's longest winning streaksince October, fuelled by optimism that the U.S. economy isstrong enough to withstand the gradual withdrawal of monetarystimulus.

Commodity related stocks were among the biggest risers aswell as the most heavily traded stocks in an otherwise quietsession that saw a little more than a quarter of the averagevolume traded with just an hour of trading left.

The basic materials sector, which contains miners and otherstocks sensitive to commodity prices, added 9 points to theindex's advance, as copper hit a four month high.

"There's a bit of volume coming back into some of thecommodity-related stocks, with commodity prices breaking throughsome important levels," Manoj Ladwa, head of trading at TJMPartners, said, adding that good data out of the United Stateswould help support commodity prices.

"The performance of the U.S. market is helping the UKmarket, and I'm maintaining a target of 7,000 for the end of theyear on the FTSE, as the momentum is there."

In another positive sign for economic growth in the world'slargest economy, U.S. jobless claims fell more than expected onThursday. This followed robust U.S. durable goods orders datareleased on Dec. 24.

The session's gains left the FTSE 1.5 percent off the 2013closing high at 6,840, which was a 13-year-high and only justover 100 points from the all-time peak.

"It feels like only a matter of time before we surpass theOctober high, and might make it there before New Year," WillHedden, sales trader at IG, said.

"Then with the all time high around 6,950, it seemsreasonable that this could be hit during the first quarter of2014."