Electric automaker Rivian on Thursday said its losses had nearly tripled to $1.7 billion in the second quarter, but that it is on the road to meeting production goals.

The California-based maker of electric trucks, SUVs, and delivery vans said that it delivered 4,467 vehicles during the quarter, generating revenue of $364 million compared to zero revenue in the same period a year earlier.

Rivian said it produced 6,954 vehicles in the first half of this year and is aiming to make a total of 25,000 vehicles by year's end.

The company ended June with a backlog of approximately 98,000 preorders from customers in Canada and the United States, according to an earnings letter to shareholders.

"Supply chain continues to be the limiting factor of our production; however, through close partnership with our suppliers we are making progress," Rivian said in an earnings letter.

"We expect to be able to add a second shift for vehicle assembly towards the end of the third quarter."

Rivian blamed its losses on investments in people and technology, along with auto production lines capable of cranking out lots of cars running at low capacity.

Per vehicle costs should drop as production line volume ramps up, Rivian said.

The company expected to post an overall loss of $5.45 billion this year due to factors including rising costs of materials and freight as well as supply line challenges, the earnings letter said.

Rivian shares slipped about 2 percent in after market trades that followed release of the earnings figures.

Tech titan Amazon was an early investor in Rivian, and committed to buying 100,000 electric delivery vans from the automaker by the end of this decade as part of an effort to reduce climate-damaging emissions by its e-commerce fleet.

Rivian said Amazon has rolled out custom electric delivery vans in more than a dozen cities in the United States.