The possibility that the United States will join France in declaring all-out war against the Islamic State (ISIS) appears more likely now as a high-ranking Democratic ally of President Barack Obama has joined hawkish Republican leaders in calling for such action.

On Friday, Democratic Sen. Chris Murphy of Connecticut sent a letter to fellow senators calling for a vote on a declaration of war on ISIS before the end-of-the-year recess in December, WND reported.

"Congress must declare war against ISIS," said Murphy, the ranking Democrat on the Senate Foreign Relations subcommittee on Near East, South Asia, Central Asia and Counterterrorism.

"Each one of us first ran for office on the promise that we wouldn't shy away from tough debates, but rather, would rise to the challenge the times demand. Now is the time to prove we meant it," he stated in his letter.

A similar call for a declaration of war on ISIS has been issued by Sen. John McCain, R-Arizona and Sen. Lindsey Graham, R-South Carolina.

Republican presidential candidate Jeb Bush has also called for a formal declaration of war against ISIS.

"We should declare war, and harness all of the power that the United States can bring to bear, both diplomatic and military, of course, to be able to take out ISIS," the former governor of Florida said on NBC's "Meet the Press" recently. He castigated the Obama administration for viewing the fight against ISIS as just a "law enforcement exercise."

Sen. Marco Rubio, another Republican presidential candidate, is also in favour of a declaration of war. "We are most definitely at war with ISIS and I'd be supportive of declaring that, whether it's formally through Congress or rhetorically," he said.

However, Democratic presidential frontrunner Hillary Clinton said she is not supporting a declaration of war on ISIS.

"If you have a declaration of war, you'd better have a budget that backs it up," she said while campaigning in New Hampshire. "I do think we have to do a better job of understanding the threat that is posed by radical Islamic jihadist groups."

At the House of Representatives, another Democratic lawmaker is also spearheading a move against ISIS but stopping short of a formal declaration of war.

Democratic Rep. Adam Schiff of California, the ranking Democrat member of the House Permanent Select Committee on Intelligence, said he will introduce a bill next month authorising the president to make full use of military force to crush ISIS.

If approved, a declaration of war on ISIS will be the first such action that the U.S. will take since World War II when it declared war on Japan.