The world's largest vaccine maker, GSK, slumped 3.2% to hit a 15-week low after missing second-quarter profit estimates under the effect of coronavirus lockdowns, dragging the healthcare index <.FTNMX4570> down 1.8%.

Kicking off the quarterly earnings season for UK banks, Barclays set aside a higher-than-expected 1.6 billion pounds ($2.07 billion) to cover a possible rise in loan losses due to the COVID-19 pandemic. Its shares fell 6.1%.

But a 7.7% jump for Next Plc helped the blue-chip FTSE 100 end in positive territory as the retailer reported a smaller-than-feared slump in second-quarter sales.

The mid-cap FTSE 250 was off 0.2%, weighed by losses in consumer discretionary, financial and tech-related stocks.

The Fed is expected to sound reassuringly accommodative at its policy review due at 2 p.m. ET (1800 GMT), followed by Chair Jerome Powell's press conference, but investors have turned wary over political wrangling between U.S. Democrats and Republicans on a coronavirus relief plan. [MKTS/GLOB][.N]

"Not much will come of (the Fed meeting) in terms of policy. That said, we think a sober assessment from the Fed or Powell could challenge risk sentiment," said Mazen Issa, senior FX strategist at TD Securities.

"With COVID cases ravaging the U.S. and the job market stalling, there is a risk that Powell sounds more bearish than dovish."

Uncertainty about global efforts to contain the pandemic stalled a three-month rally for the FTSE 100 in July. Although recent economic data has shown a revival in business activity with the lifting of nationwide lockdowns, traders are concerned about the damage from another possible shutdown.

Homebuilder Taylor Wimpey Plc shed 8.1% on saying it expected to complete around 40% fewer homes in 2020.

(Reporting by Sagarika Jaisinghani in Bengaluru; editing by Uttaresh.V and Kevin Liffey)

By Sagarika Jaisinghani and Susan Mathew