WASHINGTON - Defense lobbyists spent nearly $750,000 to help honor Obama administration officials during the first six months of the year, accounting for nearly half of the payments made then, a USA TODAY analysis of federal data shows.

Lockheed Martin, followed by three other defense contractors -BAE Systems, TriWest Healthcare Alliance and General Dynamics- reported spending the most. In many cases, the companies underwrote charity events in which the military's top brass or other key federal officials were honored or in attendance.

Overall, all lobbyists reported spending more than $1.6 million in the category of honorary expenses connected to executive branch officials between Jan. 1 and June 30. By comparison, lobbyists reported spending $2.3 million during the first six months of 2008, when President George W. Bush was in the White House. Defense contractors also topped the giving then, spending $1.8 million.

The spending, which is legal, represents another way for contractors to build relationships with the officials who have sway over their industry, said Melanie Sloan, executive director of Citizens for Responsibility and Ethics in Washington. "Most of their business is with the government," Sloan said. "Spending $50,000 is nothing if it warms up people to give them the next $100 million contract."

The analysis examined reports that lobbyists are required to file with Congress detailing donations to non-profit groups associated with public officials or payments made for events held in their honor. It did not include an additional $700,000 related to inaugural celebrations that lobbyists disclosed in separate reports.

Lockheed spent nearly $190,000 - including a $50,000 payment to the National Defense University that lists Gen. David Petraeus, the commander of U.S. forces in the Middle East, as the honoree and another $50,000 to the Coast Guard Foundation for a dinner attended by Homeland Security Secretary Janet Napolitano. Lockheed is the top recipient of Defense Department contracts. Last month, the company was awarded an $821 million contract to service Homeland Security surveillance planes.

Lockheed spokesman Jeff Adams said the payments reflect the company's long support for worthy causes. "We secure our contracts through the federal acquisition processes," he added, "not through the intervention of government officials."

Petraeus spokesman Erik Gunhus said the general has received awards at dinners recently but knew nothing of lobbyists' contributions to groups hosting the events and accepts no speaking fees.

Napolitano spokesman Matt Chandler said the secretary did nothing more than attend a dinner hosted by a Coast Guard-related non-profit and was "unaware of the contribution."

Overall, lobbyists and their employers reported more than $430,000 in expenses that list President Obama as an honoree. White House spokesman Ben LaBolt said the administration "has not authorized any corporations to make a contribution in the name of an administration official." In many cases, he added, the officials listed on lobbyists' reports either attended an event or spoke before a non-profit group and had "no contact with the event's corporate sponsors."

In some cases, top officials were at the center of the celebrations. Tyson Foods, for instance, reported a $10,000 payment in June to the Iowa Democratic Party for an event at which Agriculture Secretary Tom Vilsack, a former Iowa governor, was inducted into the party's hall of fame.

Tyson spokesman Gary Mickelson said the company was one of multiple sponsors underwriting the June event. Some company officials "spent a matter of seconds greeting" Vilsack, Mickelson added, but "none had an extended conversation with him." Chris Mather, Vilsack's spokeswoman, said the secretary "had no idea who would be there or who the sponsors would be." Vilsack's decisions, she said, "are not based on contributions."

Contributing: Paul Overberg, Brad Heath and Seung Min Kim