The White House said on Monday that it regrets and is investigating a raid by the Israeli military of a flotilla carrying supplies for Palestinians in Gaza.

A day before Israeli Prime Minister Benjamin Netanyahu is set to travel to Washington to meet with President Barack ObamaBarack Hussein ObamaDick Cheney to attend fundraiser supporting Trump reelection: report Forget conventional wisdom — Bernie Sanders is electable 2020 Democrats fight to claim Obama's mantle on health care MORE, the Israeli military raided the flotilla, killing at least nine people.

"The United States deeply regrets the loss of life and injuries sustained, and is currently working to understand the circumstances surrounding this tragedy," White House deputy press secretary Bill Burton said in a statement.

The vessels had been trying to deliver supplies to Gaza despite a blockade of the area by Israel. The New York Times reported last week that the Israeli military considered the flotilla as an act of provocation and would not allow the vessels to pass through to Gaza, setting the stage for Monday's incident.

Netanyahu is traveling in Canada Monday and is expected to address the incident — which could reignite long-standing hostilities between Israelis and Palestinians — later this morning. 

The incident could also dampen talks between Netanyahu and Obama on Tuesday, when the two were hoping to set aside the sometimes frosty relationship that had come to define peace talks between the United States and Israel.