Joe Biden pledged that the US federal government will pay the full cost of rebuilding the Francis Scott Key bridge in Baltimore, which collapsed before dawn on Tuesday after being struck by a massive cargo ship.

“It’s my intention that the federal government will pay for the entire cost of reconstructing that bridge and I expect the Congress to support my effort,” the US president said.

Asked why the government should pay and not Grace Ocean, the owners of the Singapore-registered ship, Biden said: “That could be, but we’re not going to wait for that to happen. We’re going to pay for it to get the bridge rebuilt and opened.”

Authorities said six people were unaccounted for after the accident, which sent vehicles and eight construction workers into the Patapsco river. All 22 crewmembers aboard the Dali, the ship that struck the bridge, were reported safe.

The White House said Biden had spoken to federal, state and local officials as part of the continuing response to the collapse of the bridge.

Those officials included Pete Buttigieg, the US secretary of transportation; Wes Moore, the Democratic governor of Maryland; the two Democratic US senators from Maryland, Chris van Hollen and Ben Cardin; and the mayor of Baltimore, Brandon Scott.

Moore told reporters the bridge, which was built in 1977, was “fully up to code” before being struck by the ship.

Speaking from the Roosevelt Room in the White House, Biden said: “Everything so far indicates that this was a terrible accident. At this time, we have no other indication. No other reason to believe there’s any intentional act here.”

“I know every minute in that circumstance feels like a lifetime,” Biden said, in remarks aimed at people awaiting word on the missing.

The search and rescue operation was “our top priority”, Biden said, adding: “We’re with you. We’re going to stay with you as long as it takes. You’re Maryland tough, you’re Baltimore strong.”

Saying, “We’re not leaving until this job is done,” Biden said he would travel to Baltimore “as quickly as I can”.

The president then left Washington for a campaign event in Raleigh, North Carolina. Buttigieg was due to travel to Baltimore.