By MUJIB MASHAL
The New York Times

KABUL, Afghanistan — The American military’s use of the most powerful conventional bomb in its arsenal on an Islamic State cave complex in Afghanistan has stirred up political trouble for the Afghan government, as former President Hamid Karzai on Saturday called his successor “a traitor” and declared that he wanted the Americans gone from the country.

In an interview with The New York Times, hours after he said he intended to work toward “ousting the U.S.,” a fuming Mr. Karzai said there was no justification for the United States to drop the powerful bomb in Afghanistan. The weapon, the GBU-43/B Massive Ordnance Air Blast, is referred to as the “mother of all bombs.”

He accused the American military of using the presence of Islamic State militants to turn his country into a laboratory for testing its weapons.

Mr. Karzai called President Ashraf Ghani’s government an “accomplice” that allowed and welcomed the use of the bomb. Mr. Ghani’s government had said the attack, which was said to have killed dozens of militants and destroyed three large caves in Nangarhar Province, was coordinated with the United States.

“Shame on him for saying that, shame, shame,” Mr. Karzai said. “No Afghan with self-respect would do that.” He added, “He is a traitor, a traitor.”

A spokesman for Mr. Ghani would not address Mr. Karzai’s harsh words directly. But Mr. Ghani’s office put out a brief post on Twitter, clearly aimed at Mr. Karzai: “Every Afghan has the right to speak their mind. This is a country of free speech.”

The uproar over the bombing and its meanings comes as H. R. McMaster, President Trump’s national security adviser, arrived in Kabul on Saturday for consultations with Afghan leaders as the new administration reviews its Afghanistan policy.

Afghan and American military officials described the bomb’s use as a battlefield necessity for the destruction of the Islamic State cave complex and the success of military operations. Four ground operations in the area, supported by regular, smaller airstrikes, had proven futile, they say. There have been no signs yet that the bombing caused any civilian casualties.

Other Afghan politicians have been more restrained about their views of the American bombing, with some opposed to it and others saying they supported it.

Amin Karim, the spokesman for the main faction of the Hezb-e-Islami, a conservative Islamist party with links to the insurgency, said members of his party disagreed with the strike because they believed it was carried out for American domestic political reasons and as a way to send a message to other countries at odds with the United States, rather than strictly to fight terrorism in Afghanistan.

“The goal of this attack was for beyond Afghanistan — it was for showing American power to North Korea, Syria and some other countries; it was for scaring these countries,” Mr. Amin said.

At a news conference organized by the Nangarhar governor’s office on Friday, a group of elders from the Achin district, where the bomb was dropped, expressed support for the use of such overwhelming force to eliminate the Islamic State fighters.

Atta Muhammed Noor, the powerful governor of the northern Balkh Province and a leader of the Jamiat-e-Islami, one of the largest Islamist parties, said he supported the use of the bomb as well as any “crackdown on insurgents and fundamentalists.”

Mr. Karzai said the people of eastern Afghanistan had expressed concern about Islamic State fighters crossing the border with Pakistan when the threat emerged more than two years ago, but little action was taken then. “They allowed Daesh to come and come, and empty villages of their residents and entrench themselves,” he said, using the Arabic acronym for the Islamic State. “Why did they wait for two years? Why didn’t they stop them then? All the entry points were known.”

He added: “The conclusion is that Daesh was a U.S. contractor, like DynCorp, like other U.S. companies, that they used to empty an area of its population and create a cause, create an environment, a psychological environment in which the U.S. can then test its weapon.”

Mr. Karzai, who has grown more anti-American in recent years despite having come to power with the help of the United States military, had been seen as a quiet opposition figure, albeit one intent on derailing Mr. Ghani’s government.

Even when he was in power, he was against the United States’ use of air power on Afghan villages, but analysts say they believe the latest American bombing has given him another political pretext to mobilize against the government.

Mr. Karzai said he would mobilize opposition against the American presence in his country, “from agitation, to protest, to going to the Afghan people.” But it remains unclear how much influence he now has. The current Afghan authorities forcefully blame him for the corrupt institutions they inherited and are trying to peel away the layers of patronage that once made him a powerful player.

While Mr. Ghani’s coalition government has failed to make progress in many areas and has struggled to contain the Taliban as they have seized new territory, it has been able to withstand political pressure by opponents like Mr. Karzai. It remains to be seen how much trouble he can cause.