The trial is the culmination of a long-running battle between the two over the cost of the processors that phones use to connect to mobile networks.

Apple claims Qualcomm is charging too much and that its control of the technology stifles innovation.

Qualcomm disagrees, saying that because it invented the chips it should be rewarded appropriately.

Courting costs

The row between the pair began in 2017 when Apple first filed a legal complaint. It believes that Qualcomm's dominance in phone technology lets it get away with charging high fees.

Foxconn and Pegatron, which assemble phones for Apple, have signed up to back the legal action.

Qualcomm has an extensive patent portfolio covering many of the technologies used in smartphones and derives a significant amount of its annual revenue through licence payments from phone makers.

It argues that its technology covers more than just these basic chips, called modems, and that is why it asks electronics firms to pay the fees.

Qualcomm has also accused Apple of using the legal system as a way to pay less for its technologies.

The trial is expected to last five weeks. Its opening sessions will select the jury to oversee the trial and let lawyers representing each side give opening arguments. Apple boss Tim Cook and senior Qualcomm staff are expected to testify.

Billions of dollars are at stake in the trial. Apple wants to claw back billions it claims it has overpaid. Qualcomm wants damages to punish Apple for breaching the contract it signed with the chip inventor.

If Qualcomm loses, the decision could have a significant impact on the way it operates, because other phone makers are likely to challenge the fees they pay.

The legal action between the two has kicked off investigations in many other regions and nations.

This has led to Qualcomm paying fines in China ($975m, £744m), South Korea ($853m) and Taiwan ($93m).

In early 2018. the European Commission levied a fine of €997m (£860m) against Qualcomm for allegedly breaking anti-trust laws. Qualcomm has appealed against the fine saying the case against it was "flawed".

Apple has also been hit by the fall out from the legal battle. Temporary injunctions halting the sale of iPhone 7 and 8 models were granted in Germany and China.

In March this year, a US court ruled that Apple had infringed on three Qualcomm patents covering ways to improve battery life.