NEW YORK (Reuters) - Lockheed Martin Corp (LMT.N: Quote, Profile, Research) said on Tuesday quarterly profit rose a greater-than-expected 6 percent, helped by higher sales of its electronic, information and space systems.

The world's largest defense contractor, which also runs a host of civil projects for the U.S. government, raised its full-year profit forecast, chiefly due to better projected margins at its space unit, but left it slightly below Wall Street's average forecast.

Its shares fell 3.1 percent to $103.25 on the New York Stock Exchange.

"The increase to guidance still puts the company somewhat below consensus, and could hold back shares," said Oppenheimer & Co analyst Myles Walton in a research note.

Lockheed, which makes F-16 fighter jets and Patriot missiles, but is branching further into nonmilitary services, reported first-quarter profit of $730 million, or $1.75 per share, compared with $690 million, or $1.60 per share, in the year-ago quarter.

That easily beat Wall Street's average forecast of $1.63 per share, according to Reuters Estimates.

Revenue rose 8 percent to $10 billion, helped by higher sales of its electronic and information systems, but dragged back by a dip at its plane-making unit. Analysts were expecting $9.68 billion in quarterly sales, on average.

The Bethesda, Maryland-based company raised its 2008 earnings forecast by 10 cents to a range of $7.15 to $7.35 per share. Analysts are expecting $7.36 per share, on average.

Lockheed kept its full-year sales forecast unchanged in a range of $41.8 billion to $42.8 billion. Analysts are expecting $42.85 billion, on average.

(Reporting by Bill Rigby; Editing by Brian Moss and Steve Orlofsky)