US Secretary of State John Kerry Tuesday urged lawmakers to adopt a new legal authorization to underpin military action against Islamic State militants for at least three years.

But during a heated debate, the top US diplomat came under fire from Republicans and Democrats who argued that if President Barack Obama wanted new powers to combat the jihadists, he should have drawn up a draft text to propose to the Senate.

The US-led coalition has already carried out some 1,100 airstrikes in Syria and Iraq since September targeting IS extremists in a bid to defeat the group which has seized a large territory and imposed harsh Islamic law.

So far, the Obama administration has used the existing authorization for use of military force against Al-Qaeda, the Taliban and their branches approved in the days after the September 11, 2001 attacks as the legal justification for going after IS.

Kerry told the Senate Foreign Relations committee: "I think we all agree that this discussion must conclude with a bipartisan vote that makes clear that this is not one party's fight against ISIL (IS), but rather that it reflects our unified determination to degrade and ultimately defeat ISIL."

"Our coalition partners need to know it. The men and women of our armed forces need to know it. And ISIL's cadres of killers, rapists, and bigots need to understand it."

He asked the committee to help draw up a new authorization which "provides a clear signal of support for our ongoing military operations against ISIL," referring to the group by another acronym.

Kerry also urged that the text should not limit US actions geographically to just Syria and Iraq, and suggested it should be valid for three years with room for a possible extension.

Controversially, the top US diplomat also appealed to senators not to rule out the use of ground troops.

Obama has insisted he will not send US ground troops into combat operations against IS, saying that "will be the responsibility of local forces."

"That does not mean we should preemptively bind the hands of the commander-in-chief -- or our commanders in the field -- in responding to scenarios and contingencies that are impossible to foresee," Kerry said.

While the Obama administration did not plan to carry out any operations with the 60-strong coalition outside of Syria and Iraq, Kerry argued the new legal authority should "not constrain our ability" to act in other places if needed.

"In our view, it would be a mistake to advertise to ISIL that there are safe havens for them outside of Iraq and Syria," he told senators.

Committee chairman Robert Menendez has a draft text ready for a vote, which he suggested could go ahead on Thursday.

- 13 years' legal justification -

He said he was "not comfortable" with the current reliance on the 2001 authorization and a 2002 vote for the invasion of Iraq.

"No member could have foreseen that we would still be acting under its authority 13 years later. I do not believe that it proves the authority to pursue a new enemy, in different countries, under completely different circumstances than existed 13 years ago."

The three-and-a-half-hour hearing also provided a golden opportunity for senators to bash US strategy in the region. Veteran Republican senator John McCain parried with Kerry about whose responsibility it was to draw up a war powers authorization bill." McCain also accused the administration of failing to come to the aid of the Syrian people, with 200,000 dead in the nearly four-year civil war. The moderate Syrian rebels "honestly do not understand why you won't protect them from" barrel-bombings and attacks by Syrian President Bashar al-Assad, McCain told the committee. "We're not doing anything to stop Bashar al-Assad from slaughtering them." Senator Marco Rubio also tackled Kerry saying "where is the language" from Obama setting out exactly what he needs as commander-in-chief to fight IS. "With such a clear idea of what the authorization should look like, I don't understand why the administration has not come forward and presented that ... at least as a starting point for this committee to debate," Rubio. If Obama "wants the authority to win the fight, then he's got to tell us what the fight looks like," Rubio insisted.afp, photo by al-monitor.com