By Shivansh Tiwary and Mike Stone

(Reuters) - U.S. weapons maker Lockheed Martin ( LMT ) on Tuesday reported a near 14% rise in first-quarter sales, as simmering geopolitical tensions prompt some countries to boost their defense spending, driving demand for new weapons.

Sales in its missiles and fire control unit jumped 25.3% to nearly $3 billion, boosted by strong demand for high mobility artillery rocket system (HIMARS) and guided multiple launch rocket system (GMLRS), key weapons used by Ukraine in its conflict with Russia.

Sales in its aeronautics business, the company's biggest unit that makes the F-35 fighter jets, rose 9.2% to $6.85 billion.

"These first quarter results reinforce our confidence in our ability to achieve the full year financial expectations we set in January," Lockheed CEO Jim Taiclet said in a statement.

The missile maker reaffirmed its full-year outlook, projecting net sales of $68.5 billion to $70 billion and profit between $25.65 and $26.35 per share.

Quarterly net sales rose to $17.2 billion from $15.13 billion reported last year.

Lockheed's earnings are seen as a bellwether for the arms sector. Northrop Grumman ( NOC ) and General Dynamics ( GD ) are due to report quarterly results later this week.

However, net income for the quarter ended March 31 fell to $1.55 billion, or $6.39 per share, compared with $1.69 billion, or $6.61 per share, from a year earlier, due to higher costs stemming from labor and supply chain challenges.

Last week, the U.S. Missile Defense Agency said Lockheed won a $17 billion contract to develop the next generation of interceptors to defend the United States against an intercontinental ballistic missile attack.

(Reporting by Pratyush Thakur and Shivansh Tiwary in Bengaluru; Editing by Anil D'Silva)