Washington:Donald Trump and Hillary Clinton took a giant step toward securing the White House nominations of their parties Tuesday thumping rivals in a slew of Super Tuesday primaries.

Bellicose billionaire Trump weathered a barrage of attacks from fellow Republicans to win at least seven of 11 states according to projections coming within striking distance of becoming the Republican nominee to replace President Barack Obama.

Clinton also racked up seven wins -- her strategy of embracing President Barack Obama appeared to pay dividends.

She beat rival Bernie Sanders handily across a host of southern US states -- Alabama Arkansas Georgia Tennessee and Texas -- winning big among African-American voters and reversing a 2008 primary loss in Virginia.

The former secretary of state also claimed Massachusetts in a close race.

Sanders notched wins in his tiny home state of Vermont Oklahoma Colorado and in Minnesota but he now trails heavily.

Both Trump and Clinton signaled their focus is beginning to shift to the general election.

In victory remarks Clinton attacked Trump's pledge to "make America great again."

"America never stopped being great!" she said to cheers from supporters in Miami.

"It's clear tonight that the stakes in this election have never been higher and the rhetoric we're hearing on the other side has never been lower."

Trump painted Clinton -- the former first lady senator and secretary of state -- as a Washington insider who cannot address a furious electorate's desire for change.

"She's been there for so long. I mean if she hasn't straightened it out by now she's not going to straighten it out in the next four years" he said.

A recent CNN/ORC poll found that both Clinton and Sanders would easily defeat Trump if the general election -- set for November 8 -- were held now.

But few are likely to underestimate the 69-year-old Trump after his primary rout.

Republican unease

Super Tuesday was the most pivotal day of the US presidential primary season so far with half the Republican delegates and a third of Democratic delegates needed to win the nominations up for grabs.

Trump's victories were widespread from Alabama and Georgia in the deep south to Massachusetts in the northeast to the vital battleground state of Virginia.

The scope and scale of the victories will sow terror among establishment Republicans who fear the party of Abraham Lincoln Theodore Roosevelt and Ronald Reagan could face general electoral annihilation.

While Trump's rivals Marco Rubio and Ted Cruz struggled to make the case they can still win Trump tried to defuse an intra-party feud that may be the only serious obstacle remaining on his path to the nomination.

He offered an olive branch to party leaders who are fighting a rearguard action making the case he can unify and grow the party.

"I think we'll be more inclusive and more unified. I think we'll be a much bigger party" Trump said easing up on his hallmark bombast.

Cruz Rubio on ropes

Cruz used victories in his home state of Texas with its bumper haul of delegates and in neighboring Oklahoma to argue he is the only Republican who can beat Trump.

"For the candidates who have not yet won a state who have not racked up significant delegates I ask you to prayerfully consider our coming together uniting" he said.

Rubio was projected to win only in Minnesota fundamentally undermining his claim to be the representative of mainstream Republicanism.

But he ended the day in Florida -- a clear signal that he wants to win his own home state which votes on March 15.

For good measure his campaign also announced events in Kentucky Kansas and Louisiana in an attempt to pre-empt questions about his future.

But it might be too little too late with polls showing Trump with a commanding lead nationwide.

The CNN/ORC poll gave Trump 49 percent of support nationwide with Rubio a distant second at 16 percent and Ted Cruz one point further behind.

Rubio and Cruz may both harbor long-shot hopes that Trump fails to win enough delegate support to secure the nomination outright leaving the convention to decide the nominee in July.

They may also be betting that whoever emerges strongest from a brutal 2016 campaign would be the prohibitive favorite in four or eight years' time.

AFP