(CNN) -- President Obama spoke with Libya's president after the attack that began September 11 in Benghazi, a counsel to the president told Republican senators in a letter on Thursday. Obama spoke with his counterpart on the evening of September 12, said Kathryn H. Ruemmler, counsel to the president. The senators wanted to know whether Obama called Libyan officials to help the night of the attack, which resulted in the deaths of four Americans. There are concerns that Republicans will filibuster Obama's nomination of Chuck Hagel for defense secretary if they feel they aren't getting appropriate answers to questions about the Benghazi incident.