(CNN) -- ISIS is a cancer that must be stamped out, U.S. Secretary of State John Kerry wrote Saturday in an opinion piece for The New York Times.
Kerry called the Islamist extremist group, known for beheadings, crucifixions and terror campaigns against religious and ethnic minorities, a "unifying threat to a broad array of countries" that needs to be confronted.
His article appears in the aftermath of the political uproar that engulfed the White House this week after President Barack Obama said "we don't have a strategy" on ISIS in Syria.
The Islamic State in Iraq and Syria, which calls itself the Islamic State, has grabbed headlines just as certainly as it has gobbled up territory across northern Iraq over the summer.
A companion opinion piece in the Times, co-authored by Republican Sens. John McCain and Lindsey Graham, concurred that ISIS poses a serious threat, but argue for an immediate response with a military plan at its center.
The ISIS threat only grows over time, and Obama must act with more urgency, the senators wrote.
"Doing too little to combat ISIS has been a problem. Doing less is certainly not the answer now," they wrote.
The next move
U.S. airstrikes against ISIS fighters have slowed their advance, and the Obama administration is weighing whether to expand the assault into Syria.
But, Kerry said, any decision will require a joint effort with international partners.
"With a united response led by the United States and the broadest possible coalition of nations, the cancer of ISIS will not be allowed to spread to other countries," Kerry wrote. "The world can confront this scourge, and ultimately defeat it. ISIS is odious, but not omnipotent."
McCain and Graham said the next move must include a squeezing of ISIS financing, and a successful and inclusive Iraqi government that is inclusive of Iraqi Sunnis, rather than pushing them toward terrorist groups.
"But ultimately, ISIS is a military force, and it must be confronted militarily," the senators wrote.
Obama has ordered airstrikes on ISIS in northern Iraq, but "they have been tactical and reactive half-measures," McCain and Graham wrote. "Continuing to confront ISIS in Iraq, but not in Syria, would be fighting with one hand tied behind our back. We need a military plan to defeat ISIS, wherever it is."
Building a coalition
The secretary of state's message echoes that of the White House, with both the President and Press Secretary Josh Earnest calling this week for an international coalition to confront the threat.
"Airstrikes alone won't defeat this enemy. A much fuller response is demanded from the world," Kerry wrote.
To build that coalition, Kerry, along with Defense Secretary Chuck Hagel, will meet with European allies on the sidelines of the NATO meeting in Wales next week.
Then, it's off to the Middle East to drum up support from the region.
"Already our efforts have brought dozens of nations to this cause," Kerry argued in the Times piece. "Certainly there are different interests at play. But no decent country can support the horrors perpetrated by ISIS, and no civilized country should shirk its responsibility to help stamp out this disease."