AMMAN, Jordan -- His arrest started as an invitation to coffee and ended three days later, when he walked out of a jail cell.

Ahmed Kafaween, a longtime leader of Jordan's most influential Islamic group, arrived at the provincial government building in the southern city of Karak one afternoon this month after being summoned for a chat by the police chief, who had kindly provided an escort.

"On August 20th, did you say during Friday prayer that the al-Aqsa mosque in Jerusalem was in danger of being destroyed by the Jews and that the United States supported its destruction?" Kafaween recalled being asked by an Interior Ministry agent, who was reading from a file. "Did you denounce other Arab governments for doing nothing about it?"

Kafaween said yes, then refused to sign a pledge never to do so again. He was jailed for three days as part of a nationwide roundup of 38 Islamic leaders, activists and clerics on Sept. 9 for allegedly violating a law prohibiting political commentary inside mosques.

"It was a way to stop our tongues," said Kafaween, 57, a leader of the Muslim Brotherhood and a former member of parliament. "But we can't be made to keep our mouths shut."

The detentions signal a rare crackdown by one of the Middle East's most tolerant governments, now facing uncharacteristically strident criticism from a popular Islamic movement over its alliance with the United States and diplomatic relations with Israel.

The criticism poses a challenge to King Abdullah as he pushes Western-style reforms in a country buffeted by the anger that the Iraq war has stirred in the region. Largely as a reward for Abdullah's support for the war, U.S. military and development aid to Jordan nearly tripled in 2003, to more than $1.5 billion. But that economic assistance has compromised the government in the eyes of an increasingly angry population of 5.5 million.

Signaling his concern, the king wrote an open letter to his prime minister in July that called for new preaching guidelines that "take into consideration the new variables and emphasize the compassion of the Islamic religion."

But in recent weeks, elderly Islamic leaders and members of a younger, more radical generation have stepped up criticism of government policies, delivering much of it from inside the country's well-monitored mosques. Many of the critics are young, unemployed and attracted to the social and political changes promised by Islamic politics, including a more democratic government favored by the movement's main organization, the Muslim Brotherhood.

During Friday sermons, speakers have called the monarchy "an infidel government" for its support of the United States, lashed neighboring Arab governments for their passivity and called for an end to a decade-old agreement normalizing relations with Israel, according to government officials familiar with the arrests. Other speeches have allegedly questioned the legitimacy of the monarchy.