Washington - Bosses from internet giants including Twitter and Facebook on Tuesday pressed US President Barack Obama for reforms of US spy agency snooping, adding to rising heat from the courts and American allies.Obama met a group of the country's most iconic Silicon Valley firms and spent two hours discussing the National Security Agency's clandestine electronic data mining operation, known as Prism, a participant in the meeting said.The internet company bosses fear that NSA operations have crossed constitutional lines and infringe the privacy of their customers and users in the US and abroad and could also impact their economic bottom lines."We appreciated the opportunity to share directly with the president our principles on government surveillance," said a representative of the companies after the meeting ended."We urge him to move aggressively on reform."ReformsAnother participant said the session started with a discussion on attempts to repair the Healthcare.gov website that undermined the rollout of Obama's health care reform package.Then, the president and vice president Joe Biden spent two hours going through the implications of NSA programmes.The talks focused on reforms of the Foreign Intelligence Surveillance Court, which regulates clandestine eavesdropping, electronic privacy legislation and other legal issues.The participant said the internet firm executives laid out their case for transparency in the programmes.Top executives at the talks included Sheryl Sandberg of Facebook, Tim Cook of Apple, Marissa Mayer of Yahoo, Eric Schmidt of Google and Dick Costolo of Twitter.Eight leading US-based technology companies last week called on Washington to overhaul its surveillance laws following revelations of online eavesdropping."The balance in many countries has tipped too far in favour of the state and away from the rights of the individual - rights that are enshrined in our Constitution," they wrote in an open letter to Obama.Legal tussleThe meeting came a day after a US court ruled that the National Security Agency's bulk collection of telephone records was probably unconstitutional, in the first blow of a long legal tussle over the programme.It also took place as Obama considers the findings of an intelligence review panel he set up to recommend reform of spy agency snooping in the wake of revelations by fugitive intelligence analyst Edward Snowden.The revelations of a massive US spy snooping programme on the internet have strained ties between the White House and the US tech sector.The White House said in a statement that Obama made clear his belief in an open, free and innovative internet."We will consider their input as well as the input of other outside stakeholders as we finalise our review of signals intelligence programmes."Obama is expected to address the American people in January about intelligence reforms he will undertake after considering the review panel report.Aides say he will propose some restraints on snooping on internet and telephone data but is believed to be committed to permitting NSA data mining to continue, as US spy chiefs say it is vital to their campaign against terrorism.Snowden asylumA federal judge in Washington on Monday ruled that the NSA programme was likely unconstitutional, in the first stage of a battle likely to end in the Supreme Court."I cannot imagine a more indiscriminate and arbitrary invasion than this systematic and high-tech collection and retention of personal data on virtually every single citizen," US District Court Judge Richard Leon said.Snowden, who is currently living in temporary asylum in Russia, meanwhile issued an open letter to Brazil on Tuesday, saying he could help the country's investigation into US spying.But he said that he would need refuge to do so, in a move widely interpreted as a request for asylum in Brazil."These programmes were never about terrorism: They're about economic spying, social control, and diplomatic manipulation," Snowden wrote in the letter."They're about power."The leaks by Snowden have deeply embarrassed Washington, alienated many allies and raised searching questions about the balance between individual privacy and the battle against terrorism in US society.