Rep. Darrell Issa (R-Calif.) is shifting the focus of his probe into last month’s attack in Libya squarely onto the White House.

After grilling State Department staffers about security lapses last week, the House Oversight panel chairman sent President Obama a 10-page letter on Friday demanding to know why the administration toned down the U.S. security presence in Libya while the country was still emerging from a civil war. Issa said a witness at last week’s hearing said the decision not to call back a 16-person security team over the embassy’s objection was made as part of efforts to normalize relations with Libya, a claim Democrats dispute.

“Americans … deserve a complete explanation about your administration’s decision to accelerate a normalized presence in Libya at what now appears to be at the cost of endangering lives,” Issa wrote. “These critical foreign policy decisions are not made by low- or mid-level career officials — they are typically made through a structured and well-reasoned process that includes the National Security Council at the White House.