Homeland Security Secretary Kirstjen Nielsen and Defense Secretary Jim Mattis spearheaded an agreement signed last week about how their agencies will work together on future cybersecurity challenges, Homeland Security Undersecretary Chris Krebs said last week.

The pair is also urging more cyber cooperation between military and civilian government, Krebs said.

“It was the two secretaries coming together, saying let’s make sure we understand how to best support each other’s objectives and mission and make sure our teams also understand,” Krebs told reporters after a cybersecurity conference hosted by the U.S. Chamber of Commerce Friday. “This is a top-down strategic guidance.”

Officials from the Pentagon and Homeland Security’s cyber strategy and operations division met to hammer out high-level details of that cooperation and to sign the memorandum of understanding last week, Homeland Security Assistant Secretary Jeanette Manfra said.

The strategy and operations officials will also serve as a steering committee for future cyber cooperation efforts, Manfra said.

The agreement is not classified, Manfra said, but the departments have not yet released a public draft.

The cooperation agreement came after the departments worked together on a plan for U.S. Cyber Command to come to the aid of Homeland Security and state and local election officials if the 2018 midterms were disrupted by cyberattacks or influence operations launched from Russia or elsewhere.

That assistance turned out to be unnecessary because there were no significant disruptions. The Pentagon did, however, detail 11 cyber troops to Homeland Security’s cyber operations division in advance of the election as a sort of landing team that could smooth the path for additional troops if necessary.

There are no specific future events similar to the midterm elections that the two agencies are immediately planning to cooperate on, Manfra and Krebs said. They are, however, reviewing lessons from the election to guide future cooperation.

“If there’s an event this afternoon, if there’s one tomorrow, if there’s one next week, we can pull on those same agreements and we’ve actually tested what it looks like to call in those resources,” Krebs said.

Homeland Security is in the process of identifying the parts of U.S. critical infrastructure, such as airports, hospitals and energy plants, that are most vulnerable to cyberattacks. Once those “critical functions” are identified, the department will work with the Pentagon and other sector-specific agencies on plans to protect them, Manfra said.

Sector-specific agencies include the Energy Department for possible attacks against the U.S. electrical grid and the Treasury Department for attacks that target the financial sector.

Krebs is also confident U.S. Cyber Command will coordinate with Homeland Security before significant offensive cyber operations to ensure it isn’t putting the civilian government or critical infrastructure at unnecessary risk, he said.