President Barack Obama wants the United Nations to investigate allegations of the massacre of hundreds of Syrian civilians via chemical weapons — but it is still not clear what the United States would do if the reports are confirmed.

“The United States is deeply concerned by reports that hundreds of Syrian civilians have been killed in an attack by Syrian government forces, including by the use of chemical weapons, near Damascus earlier today,” White House spokesman Josh Earnest said in a statement Wednesday. “We are working urgently to gather additional information.”

Earnest said people responsible for using chemical weapons “must be held accountable” and called on Syria to allow United Nations investigators already in Syria to investigate.

“For the U.N.’s efforts to be credible, they must have immediate access to witnesses and affected individuals, and have the ability to examine and collect physical evidence without any interference or manipulation from the Syrian government. If the Syrian government has nothing to hide and is truly committed to an impartial and credible investigation of chemical weapons use in Syria, it will facilitate the U.N. team’s immediate and unfettered access to this site,” Earnest said.

“We have also called for urgent consultations in the U.N. Security Council to discuss these allegations and to call for the Syrian government to provide immediate access to the U.N. investigative team.”

In his daily briefing, Earnest declined to detail what consequences would befall the Bashar al-Assad regime if it refuses to comply with the request or if the allegations prove to be true. He did say those responsible “will be held accountable.”

The allegations are sure to provoke a new round of questions about the president’s “red line” on chemical weapons and whether the United States will become more involved than it already is in Syria’s civil war. The administration has been attacked frequently by hawks such as Sens. John McCain, R-Ariz., and Lindsey Graham, R-S.C., for not doing more to stop the slaughter, but public opinion polls have shown little support for intervention.

The United States is providing military assistance to some of the rebels, but hawks want far more.