data, and before the outcome of the Federal Reserve's latest monetary policy meeting.
In early afternoon deals, London's benchmark FTSE 100 slid 0.28 percent to 7,010.70 points compared with Tuesday's closing level.
Frankfurt's DAX 30 index dropped 0.45 percent to 11,758 points and the CAC 40 in Paris reversed 0.62 percent to stand at 5,141.
The euro however hit a three-week dollar peak at $1.1014 on hopes that Greece will hammer out a bailout reform deal with creditors and avert a default.
The greenback also took a hit as an early US interest rate rise looks increasingly unlikely, dealers said.
Wednesday sees the release of the US government's first estimate on first-quarter economic growth, with analysts forecasting 1.0 percent, sharply down from a 2.2-percent pace in the previous three months.
"The USA looks set to be the latest country disappointed by its first quarter GDP figures," noted Spreadex analyst Connor Campbell.
"After last quarter's figure was revised down to 2.2 percent, analysts are expecting a big drop for 2015’s first quarter."
Europe's equities had dropped on Tuesday as market uncertainty resurfaced over Greece reaching a debt deal with its EU-IMF creditors.
A new Greek expert team, tasked with negotiating with the country's creditors, met Tuesday to draw up a series of reforms aimed at finally reaching a deal.
The "political negotiation team", led by the Dutch-born economics professor and junior foreign minister Euclid Tsakalotos, met late in the evening "to devise reform proposals," the finance ministry said.
Greece needs to be realistic when negotiating debt relief, Eurogroup chief Jeroen Dijsselbloem cautioned earlier Tuesday, as Athens runs out of time and money to settle a deal.
On the London stock market, miners lit up the fallers board on the FTSE 100, as investors fretted over heavy falls for copper prices.
Antofagasta shares sank 2.87 percent to 779 pence, BHP Billiton shed 2.39 percent to 1,551.50 pence and Rio Tinto dropped 1.85 percent to 2,925.50 pence.
And British bank Barclays saw its share price slide 1.63 percent to 257.05 pence on the back of a grim results statement.
The scandal-hit lender warned that fines linked to its alleged role in foreign exchange market rigging could top £2.0 billion ($3.1 billion, 2.8 billion euros), after posting plunging first-quarter net profits.
The British lender added it has set aside another £800 million for "investigations and litigation primarily relating to foreign exchange", taking the group's total provision to £2.050 billion.
Asian stock markets meanwhile slipped Wednesday after more weak US economic data raised questions about the health of the world's top economy.
Sydney plunged 1.85 percent and Hong Kong dropped 0.15 percent, but Shanghai recovered from early losses to close flat. Tokyo was closed for a public holiday.