CAIRO — Arab countries should resist funding Sunni fighters in what is turning into a cross-border war between Iraq and Syria because that support eventually could help the fast-spreading insurgency in Iraq, U.S. Secretary of State John Kerry said Sunday.

Kerry said the Islamic State of Iraq and the Levant has become a threat to the entire Mideast, and perhaps beyond.

“This is a critical moment,” Kerry said after meeting with Egyptian President Abdel-Fattah el-Sissi.

He said the group is a “threat not only to Iraq, but to the entire region.”

The U.S. is looking for ways to work with Mideast nations, most of them led by Sunni governments, to curb the group’s growth.

Some officials in the United States and the Mideast have suggested privately that Iraqi Prime Minister Nouri al-Maliki must leave office before Iraq’s Sunnis will believe their concerns will be heard by the Shiite-led government in Baghdad.

But al-Maliki has showed no indication he is willing to step down, and his political party won the most votes in national elections in April.

Both Kerry and Egyptian Foreign Minister Sameh Shoukry said it’s up to Iraqis to decide their leaders, but at the same time they said Baghdad must create an inclusive government if it hopes to quell the violence.

Shoukry, in a joint news conference with Kerry, said Egypt is worried about any spillover effects the unrest in Iraq will cause its Arab neighbors.

He said Egypt is looking to work with other countries to help the Iraqi people.