By Alasdair Reilly

LONDON (Reuters) - JP Morgan is leading the 1.2 billion euro ($1.56 billion) loan backing Finnish mobile handset maker Nokia's 1.7 billion euro acquisition of Siemens' 50 percent stake in joint-venture Nokia Siemens Networks (NSN), banking sources said.

The new financing will cover the 1.2 billion euro cash portion due at the closing of the acquisition, with the balance to be paid in the form of a 500 million euro, one-year secured loan from Siemens.

The acquisition is expected to close in the third quarter of 2013.

Nokia is rated BB- by Standard & Poor's and Ba3 by Moody's.

($1 = 0.7671 euros)

(Editing by Christopher Mangham)