WASHINGTON: US Secretary of State Mike Pompeo offered assistance to Lebanon Wednesday after the massive explosion that leveled a huge section of Beirut and left at least 113 dead.

A day after the explosion in the Lebanese capital's port, US Defense Secretary Mark Esper meanwhile played down President Donald Trump's suggestion that it was a bomb, supporting instead Lebanese official accounts that it came from 2,750 tonnes of a volatile fertilizer ingredient, ammonium nitrate, stored in warehouse.

"I'm still getting information on what happened," Esper told the Aspen Security Forum.

"Most believe that it was an accident as reported," he said.

In a call with Lebanon's Prime Minister Hassan Diab, Pompeo voiced "our steadfast commitment to assist the Lebanese people as they cope with the aftermath of this terrifying event," a State Department statement said.

He "further stressed our solidarity with and support for the Lebanese people as they strive for the dignity, prosperity and security they deserve."

The State Department only referred to a "horrible explosion," despite Trump's claim Tuesday that unnamed US generals indicated to him that "It was a bomb of some kind, yes."

The Pentagon would not confirm Trump's account.

Pompeo did not describe how the United States would help Lebanon, which was already in a deep economic crisis and seeking more than $20 billion in external funding.

The United States has been hesitant about supporting an aid package from the International Monetary Fund, insisting on reforms and the exclusion of Hezbollah, the pro-Iranian Lebanese militia and political party.