The worst U.S. recession since the Great Depression will probably end in the third quarter, but there is uncertainty over the speed and duration of the economic recovery, according to the most recent survey of private economists.

The Blue Chip Economic Indicators survey of private economists released on Monday showed about 90 percent of the respondents believed the economic downturn would be declared to have ended this quarter.

This upbeat assessment followed recent government data showing gross domestic product (GDP) contracted at a shallow 1.0 percent rate in the second quarter after sinking 6.4 percent in the January-March quarter.

Recent data, including housing and key labor market indicators, have suggested a bottoming in the recession, with the economy close to turning the corner.

Debate now centers on the speed, strength and durability of the recovery, the survey said.

It showed nearly two-thirds of respondents believed the economy was set for a U-shaped recovery, marked by below-trend growth in gross domestic product before stronger growth took hold in the second half of 2010.

About 17 percent of the respondents anticipated a V-shaped rebound, where growth pulled back to its trend rate on a sustained basis, while the same percentage fretted that a W-shaped recovery could follow, the survey showed.

In their view, GDP growth will pop higher for a quarter or two only to falter again before a lasting recovery takes hold, the survey said.

(Reporting by Lucia Mutikani; Editing by Theodore d'Afflisio)