Rivian Automotive, the electric truck startup backed by Amazon and Ford, is close to raising a new round of funding valuing it at about US$25bn, according to Bloomberg sources.

Several existing Rivian investors are participating in the round, which will raise several billion dollars, the sources told Bloomberg.

Existing investors include Amazon, T Rowe Price Group, BlackRock, Soros Fund Management, Coatue, Fidelity Investments and Baron Capital Group.

The funding isn't finalized and details could still change, Bloomberg reported.

A Rivian representative told Bloomberg: "We are focused on delivering the R1T, R1S, and Amazon delivery vehicles in 2021. We often speak to investors, and we have no announcement to make at this time."

The new funds would add to the $6bn Rivian had already raised to date, making it one of the most-well capitalised EV makers, Bloomberg said.

The startup was founded in 2009 by RJ Scaringe, a Massachusetts Institute of Technology graduate with a doctorate in mechanical engineering who is chief executive officer.

Deliveries of its first batch of pickups, which Rivian hasn't quantified but has said are sold out, are due to start in June. If it sticks to that timeline, Rivian has a shot at being the first company to bring a battery electric pickup  - one of the most anticipated vehicle categories - to the US market, Bloomberg said.

The R1T faces an onslaught of competition from new and established automakers and is aiming for an untested market.

While pickups are best sellers in the US, it's unclear how much demand there is for battery-powered trucks, Bloomberg said.