A looming fight over military budgets if Democrats regain power in Congress may handicap growth at U.S. defense contractors that have benefited from GOP spending.

While robust backlogs at the largest firms should shield profits in the months through September 2019, the period for which Trump recently signed a $674 billion spending bill, the possible shakeup coupled with the pending expiration of a two-year budget agreement threatens his plans for $700 billion in defense funding in fiscal 2020.

Lockheed Martin, the Bethesda, Md.-based contractor building the F-35 fighter jet — the most expensive weapon in U.S. history, is “always mindful” of potential budget tightening but is confident that defense funding would remain high given the White House’s desire to “continue to modernize our military,” Chief Executive Officer Marillyn Hewson told investors last week.

Lockheed profit rose 53 percent to $1.47 billion during the third quarter, and earnings increased an average 38 percent at the firm and rivals from General Dynamics to Raytheon, Northrop Grumman and Boeing. Sales surged an average 14 percent.

Several of the contractors boosted their full-year profit targets, some after receiving lucrative contracts in the second half of 2018. Boeing alone won $13 billion in work in late summer, a figure that helped increase the Chicago-based planemaker's revenue 4 percent to $25.1 billion.

Defense funding is a "year-to-year battle as you know," Chief Executive Officer Dennis Muilenburg said on Boeing's earnings call. "But we've seen more and more signs of sustained, long-term stable defense budgets in the U.S.”

Northrop Grumman profit rose 78 percent in the third quarter to $1.1 billion, while General Dynamics earnings increased 11 percent to $851 million. With a strong order pipeline, those profits could continue to grow well into 2019. The order backlog at Raytheon alone widened 13 percent in the quarter to $41.6 billion, a record for the firm.

The Trump administration's increasing attention to the space industry is also spurring new business opportunities. Boeing completed its acquisition of Millennium Space Systems, which operates in the rapidly growing small satellites industry, in September.

And revenue at Northrop's recently acquired Innovation Systems unit — which builds launch vehicles, propulsion systems, satellites, and other aerospace products — was $1.4 billion in its first full quarter of results. Chief Executive Officer Kathy Warden attributed the performance to "continued strong growth" in the business's markets.

Sales at Lockheed Martin's space segment rose 11 percent in the quarter to $2.56 billion.