The wounded Syrian government troops were returning to their country in trucks escorted by Iraqi soldiers. They almost had reached the border, near the frontier town of Akashat, when the attackers struck.

Regional intelligence officials saw the March 4 ambush, which left 48 dead, as evidence of a growing, cross-border alliance between two powerful Islamic extremist groups — al-Qaida in Iraq and Jabhat al-Nusra or Nusra Front in Syria. Nusra Front is the most effective rebel faction fighting President Bashar Assad’s regime, and the U.S. designates both Sunni jihadi groups as terrorist organizations.

Iraqi intelligence officials say the burgeoning cooperation is pumping new life into the Sunni insurgency in their country. They point to nearly 20 car bombings and suicide attacks that killed over 65 people, mostly in Baghdad, on the eve of the 10th anniversary of the U.S.-led invasion of Iraq last month.

The alliance is also nurturing Nusra Front, which emerged as an offshoot of Iraq’s al-Qaida branch in mid-2012 to battle Assad’s regime as one of a patchwork of disparate rebel groups in Syria. Nusra Front’s presence on the battlefield complicates desperately needed international support for Syrian rebels, because foreign backers do not want to bolster Islamic extremist groups.

Two Iraqi intelligence officials said the cooperation reflected in the attack on the wounded Syrian troops prompted their government to request U.S. drone strikes against the fighters. They spoke on condition of anonymity because they were not permitted to talk to reporters about the subject.

A U.S. official confirmed that elements within the Iraqi government had inquired about drone strikes. The official said the U.S. was waiting to respond until the top level of Iraqi leadership makes a formal request, which has not happened yet.

Iraq is also turning elsewhere for assistance. Ministry of Defense spokesman Mohammed al-Askari said that in Iraq’s last weapons deal with Russia, Baghdad requested aircraft and heavy weapons to try to seize control of the Iraqi-Syria border region where the groups are operating.

The two Iraqi intelligence officials said the jihadi groups are sharing three military training compounds, logistics, intelligence and weapons as they grow in strength around the Syria-Iraq border, particularly in a sprawling region called al-Jazeera, which they are trying to turn into a border sanctuary they can both exploit.

It could serve as a base of operations to strike either side of the border.