Two tech titans will square off in court today in a closely watched trial over control of the US smartphone and computer tablet markets.

Apple filed a lawsuit against Samsung last year alleging the world's largest technology firm's smartphones and tablets are illegal knockoffs of its popular iPhone and iPad products.

Apple is demanding $2.5 billion in damages from the South Korean company, an award that would dwarf the largest patent-related verdict to date. 

Samsung counters that Apple is doing the stealing and that some of the technology at issue - such as the rounded rectangular designs of smartphones and tablets - has been industry standard for years.

The US trial is just the latest skirmish between the two over product designs. A similar trial began last week, and the two companies have been fighting in courts in the UKand Germany. The case is one of some 50 lawsuits among myriad telecommunications companies jockeying for position in the burgeoning $219 billion market for smartphones and computer tablets.

US District Judge Lucy Koh in San Jose last month ordered Samsung to pull its Galaxy 10.1 computer tablet from the US market pending the outcome of the trial, though the judge barred Apple lawyers from telling the jurors about the ban.

Experts said a verdict in Apple's favour could send a message to consumers that Android-based products such as Samsung's are in legal jeopardy.

A verdict in Samsung's favour, especially if it prevails on its demands that Apple pay its asking price to certain transmission technology it controls, could lead to higher-priced Apple products.

Legal observers say it is rare that a patent battle with so much at stake does not settle short of a trial. Court-ordered mediation sessions attended by Apple's chief executive Tim Cook and high-ranking Samsung officials failed to resolve the legal squabble, leading to a highly technical trial of mostly expert witnesses opining on patent laws and technology.

Cook is not on the witness list and is not expected to testify during what is expected to be a four week-trial.

They say it also appears that Apple was motivated to file the lawsuit, at least in part, by its late founder's public avowals that companies using Android to create smartphones and other products were brazenly stealing from Apple.

To that end, Samsung's attorneys made an unsuccessful pitch to have the jury hear excerpts from Steve Jobs' authorised biography.

"I will spend my last dying breath if I need to, and I will spend every penny of Apple's $40 billion in the bank, to right this wrong, I'm going to destroy Android, because it's a stolen product," Jobs is quoted as saying in Walter Isaacson's book "Steve Jobs" published in November. "I'm willing to go thermonuclear war on this." But the judge barred those statements in a ruling earlier this month.

Apple lawyers argue there is almost no difference between Samsung's products and Apple's and that Samsung's internal documents show it copied Apple's iconic designs and its interface.

Samsung denies the allegation and counter-charges that Apple copied its iconic iPhone from Sony. Samsung lawyers noted that the company has been developing mobile phones since 1991 and that Apple jumped into the market only in 2007.