WASHINGTON (AP):

President Barack Obama says his executive actions blocking the deportation of millions living illegally in the US go as far as the law allows. But Hillary Rodham Clinton says that if she becomes president, she would go even further.

Clinton's aggressive stance reinvigorates the debate over the scope of presidential powers, which has become a flashpoint in Washington's politically fraught immigration fight. It also raises questions about the legality of Clinton's proposals and sets up a potential conflict between the Democratic front-runner and the Obama White House.

executive measures

The president unveiled executive measures last fall that spare up to five million people, mostly parents and the young, from deportation. The administration also set new enforcement priorities that could make it easier for many more people in the US illegally to stay in the country.

Obama's measures marked the most sweeping changes to the US immigration system in nearly three decades, and followed a fruitless six-year bid to get Congress to act on sweeping legislation. The status of America's fractured immigration laws has become a top issue in recent presidential campaigns, in part because of the growing power of Hispanic voters.

unilateral move

Clinton, speaking to young immigrants in Nevada on Tuesday, vowed to protect Obama's actions, which could also be voided by future presidents. In a surprise to many supporters, Clinton added that she would move unilaterally to let even more people stay in the country if Congress didn't act on broad legislation.

"I would do everything possible under the law to go even further," Clinton said. She specifically raised the prospect of stemming deportations for parents of 'dreamers' those who were brought to the country illegally as children. They were not covered under Obama's executive actions.

More than 70 per cent of Hispanic voters backed Obama in the 2012 election. Clinton's focus on immigration early in her campaign underscores her desire to maintain that advantage over Republican rivals, all of whom oppose Obama's use of presidential powers to block deportations.