* FTSE 100 index falls 0.2 pct by midday trading
* Miners take most off FTSE 100
* Tui Travel falls as key investor sells stake
By Atul Prakash
LONDON, Nov 22 (Reuters) - Britain's top share index edged lower by midday on Friday and headed for a third straight week of losses. Mining companies took the most off the index on concern about their earnings.
The blue-chip FTSE 100 index was down 16.06 points, or 0.2 percent, at 6,665.27 by 1154 GMT. It is down 0.5 percent this week but still up 13 percent so far this year.
The index came under pressure as the UK mining sub-index fell 1.9 percent, making it the sector losing the most. Anglo American dropped 2.5 percent, BHP Billiton 2.3 percent and Rio Tinto 1.6 percent.
"The general consensus seems to be that the big miners might find their earnings under pressure as costs remain static and perhaps commodity prices gradually weaken," said Tim Whitehead, investment manager at Redmayne-Bentley. "There has been a little bit of rotation out of the mining sector.
"With the Dow and the S&P 500 hitting new highs this week, a little bit of caution is creeping in. The market is in a tight range. However, it seems to be reasonably underpinned. We could see good demand at pullbacks."
The FTSE rose earlier in the day after Bank of England officials reaffirmed monetary policy would remain accommodative for some time. The index also tracked the U.S. market, where the Dow Jones Industrial Average closed above 16,000 for the first time.
A sharp decline in some stocks put pressure on the market. Tui Travel fell 5.3 percent on news Norwegian shipping magnate John Fredriksen had sold his entire stake in the British company.
The FTSE 100 remained firmly stuck in the 200-point range of the past month - half as big as that of the previous month.
"I can't rule out a deeper dip but see any weakness as corrective against the wider uptrend," said Ed Blake, a technical analyst at Informa Global Markets. "(I) am looking for the current slide to resolve bullishly into Christmas."
Noting strong support for the index in the 6,504.27-6,526.22 area, Blake said "a resumption of the long-term uptrend is then favoured through 6,732.10 (Nov. 18 high) targeting 6819.86."
Whitbread rose 3 percent and William Hill 2.4 percent on analyst upgrades. Tullow Oil gained 1.4 percent after reporting an oil discovery in Kenya.
Analysts said the shares could trade in a tight range for the rest of the year and investors would need to be selective.
"I look for stable companies with good balance sheets and reliable dividends and am sticking with the big blue-chip names at the moment," Whitehead of Redmayne-Bentley said. "Stocks like Morrison Supermarkets, Unilever and Royal Dutch Shell are looking quite attractive."