In the final quarter of 2017, Tesla delivered only 1,550 of its mass-market Model 3 sedan, well below its production target of 20,000 such vehicles per month that chief executive Elon Musk promised last summer when the car first went into production.

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In a securities filing Wednesday, the US e-car pioneer said it now expected to hit a Model 3 production level of 5,000 cars per week by the end of the second quarter rather than at the end of the first quarter.

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The delay comes only two months after it last pushed back the 5,000-a-week target by a full quarter. But the company nevertheless claimed it had made "major progress addressing Model 3 production bottlenecks," saying the production rate had "increased significantly" towards the end of the quarter.

"In the last seven working days of the quarter, we made 793 Model 3's, and in the last few days, we hit a production rate on each of our manufacturing lines that extrapolates to over 1,000 Model 3's per week," the company added.

Shares plunge

Tesla's first lower-cost, high-volume car is crucial for the Palo Alto, California-based carmaker to becoming a profitable company after years of running up steep losses.

It has more than 500,000 potential buyers on the waiting list for the Model 3. In a statement, the company thanked those buyers "who continue to stick by us while patiently waiting for their cars."

Tesla now hopes to achieve a "slightly more gradual ramp" during the first quarter of 2018, with a weekly rate of about 2,500 Model 3 vehicles, and reaching the 5,000-mark by the end of the second quarter.

The first Model 3 cars rolled off the production line in July last year. But Tesla has since been facing major problems on mastering the complexity of mass-producing the $35,000 apiece vehicle.

The company said was focusing on quality and plant efficiency, not just meeting volume targets. But Tesla's latest production headaches with the Model 3 wiped nearly 2 percent of its shares  in after-market trading on Wednesday, leaving them 20 percent below their peak of last summer.

uhe/nz (Reuters, AFP, AP)