UPDATE 1-Greek debt buyback attracts 31.8 bln euros - source

(Adds quote from banker involved in operation)

BRUSSELS, Dec 11 (Reuters) - Greece's debt buyback attracted bids totalling 31.8 billion euros, a senior euro zone official said on Tuesday, but the average price paid for the bonds was slightly above expectations meaing the total debt reduction will be less than planned.

A banker involved in the operation confirmed the figures, saying that the average price paid for the bonds purchased was 33.5 cents on the euro.

The marginally higher-than-forecast price means that the operation had a shortfall of around 450 million euros and the total debt reduction will be around 9.5 percentage points, less than the targeted 11 percentage points.

When that is factored in, it indicates that Greece's debt-to-GDP ratio will fall to around 126.6 percent in 2020, slightly above the 124 percent that was agreed with the IMF last month, a figure that also takes into account further contingent measures.

While slightly below expectations, officials said it would not take much to close the gap.

Euro zone finance ministers will discuss the issue in a conference call later on Tuesday, several people said.

The banker, who spoke on condition of anonymity, said it would not be difficult to find further bondholders who might sell their holdings to make up the shortfall.

"The amount could be tapped from German bad banks -- they have not tendered all of their holdings," the banker said.

"The IMF will not let go easily knowing that there are bonds that haven't been tendered. Greek banks offered almost all they had."

Officials said they did not expect euro zone finance ministers to issue a statement after their conference call. Instead they will meet in Brussels on Thursday morning to discuss the results of the buyback operation.

(Reporting by European bureaus, writing by Luke Baker; editing by Rex Merrifield)