(CNN) -- President Obama is "deeply concerned" about the growing number of deadly attacks on U.S. forces by Afghan security forces, and plans to contact the Afghan president to discuss taking tougher actions, he said Monday. "I'll be reaching out to President (Hamid) Karzai," Obama told reporters at the White House, adding, "We've got to make sure that we're on top of this." Obama spoke Monday with Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff. The top U.S. military official is in Afghanistan for meetings with coalition and Afghan leaders, including Gen. John Allen, commander of NATO forces, and Afghan Army Gen. Sher Mohammad Karimi, Dempsey's counterpart in the country.
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NEW: President Obama says he will talk to President Karzai about the issue
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NEW: Obama spoke with the chairman of the Joint Chiefs of Staff, who is in Afghanistan
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Only about 10% of the attacks are related to the insurgency, military officials say
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"Vulnerability of local police to (terrorist) influence is great," the U.S. top military official says
An incident Sunday brought the death toll in attacks by Afghan military and police personnel this year to 40, according to @placeholder military officials.