He said it would be up to others to weigh on intelligence matters.
Israel said its fighter jets struck a multi-storey building "which contained military assets belonging to the intelligence offices of the Hamas terror organization."
Israeli Prime Minister Benjamin Netanyahu told CBS broadcaster on Sunday that Israel would provide such proof through "intelligence services". It was not clear whether Israel provided that to the United States.
Blinken said the United States was working round the clock to help put an end to the violence but gave few details.
"We're not standing in the way of diplomacy, on the contrary we are exercising it virtually non-stop," Blinken told a news conference with Denmark's foreign minister when asked why the United States had blocked a UN Security Council statement condemning Israel's military response.
Washington, a strong ally of Israel, has been isolated at the United Nations over its objection to a public statement by the Security Council because it worries it could harm diplomacy behind the scenes.
Blinken said Israel has the right to defend itself, but that he had been alarmed that journalists and medical workers had been put at risk, in particular after Israel destroyed the tower block in Gaza housing a number of media outlets.
IDF SPOKESPERSON Brig.-Gen. Hidai Zilberman on Sunday deflected criticism of the military's actions in the Gaza Strip, particularly the bombing of the Al Jala building with media offices on Saturday.