"Afghan and foreign troops closely coordinated this operation and were extra cautious to avoid any civilian casualties", it said. He told USA lawmakers the current troop level was insufficient and there was a "shortfall of a few thousand" advisers to train the Afghans.
Afghan officials said 36 militants were killed in the strike in Nangarhar province, near the Pakistan border.
Afghanistan's ambassador to the US, Hamdullah Mohib, said the colossal MOAB was dropped after fighting had intensified over the last week. "The decision to drop the MOAB in eastern Afghanistan sends a clear message that the USA is committed and determined to defeating ISIS and other terrorist organisations in Afghanistan", said Senator Jim Inhofe, senior member of the Senate Armed Services Committee.
"The United States takes the fight against ISIS very seriously and, in order to defeat the group, we must deny them operational space, which we did", Spicer said.
Thursday's strike came as US President Donald Trump dispatches his first high-level delegation to Kabul, amid uncertainty about his plans for the almost 9,000 American troops stationed in Afghanistan.
But fierce opposition among Afghans also surfaced.
The bomb, known officially as a GBU-43B, or massive ordnance air blast weapon, unleashes 11 tons of explosives.
"The Secretary General and I had a productive discussion about what more North Atlantic Treaty Organisation can do in the fight against terrorism", Trump said.
The statement said Afghan forces will continue to fight against the terrorist groups in close coordination with USA forces in the country.
Mr Crowley, a former U.S. air force colonel, said the bomb was "like creating a minor quake in that particular area".
General John Nicholson, the head of USA and worldwide forces in Afghanistan, said the bomb was used against caves and bunkers housing fighters of the Islamic State in Afghanistan, also known as ISIS-K.
Nine metres (30 feet) long, with a diameter of one metre, according to GlobalSecurity.org, it is the largest-ever satellite-guided, air-delivered weapon in history.
The MOAB is a custom-made Air Force weapon that has been in the arsenal for more than a decade but had never been used on the battlefield, although it was available throughout the Iraq war.
"Although the MOAB weapon leaves a large footprint, it is discriminate and requires a deliberate launching toward the target", the review said, adding, "It is expected that the weapon will have a substantial psychological effect on those who witness its use".
"This is the right munition to reduce these obstacles and maintain the momentum of our offensive against ISIS-K", General Nicholson said in a statement.
Achin district governor Esmail Shinwari said the bomb landed in the Momand Dara area of Achin district.
General John Nicholson, the head of U.S. and global forces in Afghanistan, said the bomb was used against caves and bunkers housing fighters of the Islamic State in Afghanistan, also known as ISIS-K.