WASHINGTON (Reuters) - Lockheed Martin Corp (LMT.N: Quote, Profile, Research) has agreed to pay $10.5 million to settle a civil investigation into billing problems with the company's Titan IV rocket.

Lockheed said it was pleased with the resolution of the matter, and said it had voluntarily disclosed errors in billing requests from 1998 to 2001 after they were discovered during an internal review.

Company spokeswoman Cheryl Amerine said the billing problems resulted in early payments, but they would have been due on the contract at a later point in time.

The billing errors were the subject of an investigation by the U.S. Attorney's office in Los Angeles, which said in a statement on Monday that Lockheed obtained "excessive progress payments by manipulating its billings."

Prosecutors said the amount was about double the interest Lockheed would have received by holding the premature payments.

Lockheed's Amerine said the company was committed to following established billing procedures on its more than 3,000 government programs.

Lockheed "will not hesitate to initiate our own reviews and disclose to the government any errors uncovered by those reviews or any information that may cause doubt or concern in the integrity of our process," Amerine said.

The Titan IV rocket was retired in 2005, when it was replaced by the Titan V and Delta IV rockets.

(Reporting by Andrea Shalal-Esa; Editing by Tim Dobbyn)