Two senior US Republican senators have said they want changes to the controversial 9/11 bill to narrow the scope of possible lawsuits, as the new law allows victims' families to sue Saudi Arabia over its alleged links with the perpetrators of the 11 September, 2001 attacks.

Linsdey Graham and John McCain, two of the Republican Party's congressional foreign policy leaders said on Wednesday (30 November) that they want the law to sue a government only if it "knowingly" engages in financing or sponsoring terrorism or terror groups.

"All we're saying to any ally of the United States [is], you can't be sued in the United States for an act of terrorism unless you knowingly were involved, and the same applies to us in your country," Graham said in a Senate speech, Reuters reported.

They argued that the law could have unintended consequences hurting the US.

"It protects the United States in its efforts to defend itself in a very dangerous world," Graham said. "We don't want to be sued under those circumstances."

In September, Congress overwhelmingly overruled President Barack Obama's veto of the Justice Against Sponsors of Terrorism Act (Jasta), also known as the 9/11 bill. Obama had warned the bill could lead to retaliatory lawsuits from other countries. However, lawmakers soon said they wanted the scope of the law to be narrowed in a bid to ease concerns about its potential effect on Americans living abroad – a primary reason why Obama was thought to have vetoed the bill.

But the law also grants an exception to the legal principle of sovereign immunity in case terror activity takes place on US soil. It clears the way for lawsuits seeking damages from the Saudi government.

It is not clear if Graham and McCain's proposal would bring changes to the law, but a group of victims' families have already immediately responded strongly opposing it. They said late on Wednesday (30 November) that fixing the law now would weaken and "effectively gut" Jasta, according to the Associated Press.

Terry Strada, national chair of 9/11 Families and Survivors United for Justice Against Terrorism, said the senators were seeking to "torpedo" the law by making changes allegedly demanded by Saudi Arabia's lobbyists.

"We have reviewed the language, and it is an absolute betrayal," Strada said. "The president-elect has made his support for Jasta crystal clear, and there is zero risk that he will support this kind of backroom backstabbing of the 9/11 families."

Donald Trump, who will take over from Obama on 20 January, had called the president's veto of Jasta "shameful". He said in September it would "go down as one of the low points of his [Obama's] presidency".

The US Congress overruled President Barack Obama’s veto of the Justice Against Sponsors of Terrorism Act (Jasta), also known as the 9/11 bill in September Joshua Roberts/ Reuters