White House officials raised concerns about online piracy legislation pending in Congress that Google and Facebook have decried as heavy-handed.

However, Hollywood studios and music labels say it is needed to save US jobs.

In a blog posting, three advisers to President Barack Obama said they believed the proposed Stop Online Piracy Act (Sopa) and other bills could make businesses on the Internet vulnerable to litigation and harm legal activity and free speech.

'Any effort to combat online piracy must guard against the risk of online censorship of lawful activity and must not inhibit innovation by our dynamic businesses large and small,' said the officials, including White House cyber-security czar Howard Schmidt.

The House of Representatives' Sopa bill aims to crack down on online sales of pirated American movies, music or other goods by forcing Internet companies to block access to foreign sites offering material that violates US copyright laws.

US advertising networks could also be required to stop online ads and search engines would be barred from directly linking to websites found to be distributing pirated goods.

The search engine Google has repeatedly said the bill goes too far and could hurt investment. Along with other Internet firms such as Yahoo!, Facebook, Twitter and eBay, it has run advertisements in major newspapers urging Washington lawmakers to rethink their approach.

Proponents of stricter piracy rules reacted strongly to Saturday's White House statement, which darkened prospects for legislation already expected to struggle to clear Congress in an election year.

'It is not censorship to enforce the law against foreign thieves,' said Lamar Smith, a Texas Republican who chairs the House judiciary committee. He estimated intellectual property industries provide 19 million high-paying US jobs and account for more than 60 percent of American exports.

'Congress cannot stand by and do nothing while some of America's most profitable and productive industries are under attack,' he said in a statement responding to the White House.

Smith, in an interview with Reuters on Thursday, had vowed to press ahead with the bill in spite of criticism from Google and others and said he thought it would pass the House, where Republicans have a majority. - Reuters