By Kevin Krolicki and David Bailey

DETROIT (Reuters) - General Motors Corp GM.N reported a $15.5 billion (7.8 billion pounds) quarterly loss on Friday as North American sales dropped by 20 percent and resale prices for SUVs coming off lease plunged.

GM shares fell as much as 11 percent in reaction to the automaker's announcement of the much bigger-than-expected quarterly loss, the third-largest in its 100-year history.

The No. 1 U.S. automaker burned through $3.6 billion in cash in the quarter as it cut factory output by 27 percent in response to an accelerating downturn in its home market that has hammered sales of its trucks and SUVs.

GM executives declined to say how much cash the automaker expects to burn in the second half of this year but said the company needs a minimum of $11 billion to $14 billion to run its global operations.

GM ended the second quarter with $21 billion in cash and $5 billion in undrawn credit. It has since drawn down a revolving loan facility by $1 billion.

"GM does not face imminent liquidity concerns but we think will need to raise liquidity over the next 12 to 18 months," J.P. Morgan analyst Himanshu Patel said in a note.

GM has said it has the cash needed through 2009 even assuming industry-wide U.S. auto sales drop by some 13 percent this year and hold flat next year, as many analysts now expect.

Chief Financial Officer Ray Young said GM is on track to free up $15 billion in liquidity with cost-cutting, asset sales and new borrowing under a July plan intended to assure investors that the automaker can ride out the downturn.