(Reuters) - Tesla shares jumped 5% on Friday on expectations that its electric-vehicle charging system would become an industry standard after General Motors joined cross-town rival Ford in agreeing to use the Tesla Supercharger network.

The Elon Musk-led automaker was on course for its eleventh straight session of gains, which would mark its longest winning streak in 2-1/2 years, if premarket gains hold. Tesla was also the third-most traded U.S. stock across exchanges.

Already the world's most valuable automaker, Tesla was set to increase its market value by more than $30 billion to about $780 billion.

Shares of General Motors, whose valuation is much lower at $49.8 billion but sells millions more vehicles annually, rose 3.5%.

The rare partnership among the automakers ensures that nearly 70% of the U.S. EV market will now be on Tesla's North American Charging Standard, which is expected to put pressure on other companies to ditch the current industry-standard CCS and build out their networks using Tesla's system.

"We estimate Ford and GM combined could add another $3 billion to services EV charging revenue for Tesla over the next few years in another accretive poker move by Musk & Co," said analysts at Wedbush Securities, raising their price target on Tesla's shares to $300.

That is nearly 30% higher than Tesla's last close. The stock's forward 12-month price-to-earnings ratio is 60.46, compared with GM's 5.29 and Ford's 7.94.

The brokerage added that the move will also "aid GM's objective to expand charging access to more than 134,000 chargers available to GM EV drivers today through the company's Ultium Charge 360 initiative and mobile apps".

Both Detroit automakers have struggled to escape from Tesla's shadow in the EV race. They are expected to lag well behind EV market leaders Tesla and Volkswagen through 2028, according to data provided by AutoForecast Solutions.

(Reporting by Aditya Soni; Editing by Shounak Dasgupta)