BP oil leak is 'worst US environment disaster'

US lawmakers and the American public are demanding BP and the Obama administration do more to save the US Gulf Coast from an out-of-control oil spill that one congressman called an "environmental crime".

The failure of a "top kill" technique attempted by British-based BP to try to seal its leaking Gulf of Mexico well has unleashed a surge of anger and frustration that poses a major domestic challenge for President Barack Obama.

Obama, who has called the leaking BP well a "manmade disaster", is trying to fend off criticism that his administration acted too slowly in its response to the nearly six-week-old spill, now known to be the worst in US history.

The crisis could swell into a political liability for the Democratic president as his administration and party, bloodied by bruising healthcare and economic policy debates, head towards key mid-term Congressional elections in November.

"This is probably the biggest environmental disaster we have ever faced in this country," top White House energy adviser Carol Browner told NBC's "Meet the Press."

British energy giant BP and the entire US oil industry face more and more probing questions about why safety backups did not accompany their relentless hunt for more oil in ever deeper offshore waters.