* Oils, miners fall on easier commodity prices
* Banks under pressure on continuing break-up fears
* Drugmakers in demand ahead of results
By Tricia Wright
LONDON, Oct 28 (Reuters) - Britain's top share index was down 1.3 percent in early trade on Wednesday, mirroring a weakness in Asian markets and with heavyweight oils and miners suffering from commodity price falls, while banks also weighed.
At 0913 GMT, the FTSE 100 was off 65.93 points at 5,135.04, flirting with a near three-week low, after it closed 0.2 percent higher at 5,200.97 the previous session.
"Everybody is on tenterhooks ahead of the U.S. third-quarter GDP numbers tomorrow afternoon," said Jim Wood-Smith, head of research at Williams de Broe.
"After we got the very weak UK number on Friday, if we get that backed up by a disappointing U.S. number it's going to put some serious question marks over the viability of the perceived recovery," he said.
Miners took the most points off the index, reflecting lower metal prices as doubts over the demand outlook resurfaced.
Vedanta Resources shed 2.7 percent, impacted by a Barclays Capital downgrade to "equal weight", with Rio Tinto, BHP Billiton, Kazakhmys and Lonmin 2.1 to 2.5 percent lower.
Energy stocks fell, having rallied strongly on Tuesday on the back of BP's stellar numbers, with crude 0.6 percent weaker.
BG Group was the worst off in the sector, down 2 percent, after it posted a 44 percent drop in third-quarter net profits to 484 million pounds as gas and oil prices plummeted, although its underlying profits beat forecasts.
Broker downgrades put pressure on BP, off 1.2 percent, with Citigroup cutting its rating for the oil major to "hold" from "buy" as thinks that the firm's operational recovery is peaking.
Royal Dutch Shell lost 0.7 percent and Tullow Oil was 1.6 percent easier.
BANKS EXTEND DECLINES
The banking sector extended its decline, with the break-up of Dutch financial services group ING continuing to weigh heavily on its UK peers.
Investors were unsettled by mounting fears over the disposals which government-backed banks will have to make in order to satisfy the European Commission.
Royal Bank of Scotland fell 2.1 percent, Lloyds Banking Group dropped 1.6 percent, Barclays shed 1.7 percent, and Standard Chartered fell 0.4 percent.
Lloyds Banking Group, Royal Bank of Scotland and Northern Rock will be broken up and parts of their businesses sold off to create three new banks, the Independent newspaper said, quoting government sources.
Investors were also uneasy as they awaited further developments on regulatory change following moves across the Atlantic.
The Obama administration unveiled a landmark bill to tackle systemic risk in the economy and won congressional committee approval for a measure to expose hedge funds to more scrutiny.
Life insurers were also under pressure, with Aviva, Legal & General, Old Mutual and Standard Life down 1 to 1.5 percent.
Prudential, Britain's largest insurer, shed 1.2 percent. It reported a better than expected 9 percent drop in third-quarter sales on Wednesday, as its Asian region and U.S. businesses offset weakness at home.
Elsewhere, British American Tobacco, the world's second-biggest cigarette maker, slipped 1.3 percent after posting a 3 percent dip in underlying nine-month sales volumes as it said trading conditions had deteriorated.
Drugmakers were in demand, with GlaxoSmithKline putting on 0.6 percent ahead of its third-quarter results due at 1200 GMT, and Shire, which reports on Friday, up 0.7 percent.
Positive broker sentiment helped lift BT Group, which rose 0.4 as Barclays Capital initiated coverage on the telecoms carrier with an "overweight" rating as it started the European telecoms sector with a positive view. (Editing by Greg Mahlich)