BOSTON (Reuters) - It was to be the biggest mosque in the northeastern United States, a center of worship for Boston's 70,000 Muslims and a milestone for America's Muslim community.

Instead, construction of the $24.5 million center has been stalled by lawsuits and a deepening row between Jewish and Muslim leaders that reflects broader suspicions facing American Muslims after the September 11 attacks.

Jewish leaders charge that former and current officials in the Islamic Society of Boston, which is building the 70,000-sq- ft (6,500-square-meter) mosque, are linked to terrorist groups and have failed to distance themselves from radical Islam and anti-Jewish statements.

The Islamic Society denies any connection to terrorism and considers itself victimized by a campaign to taint the mosque with accusations of ties to radical Islamic teachings. The society says it has repeatedly distanced itself from anti-Jewish statements by some of its leaders.

Among Jewish concerns is whether a former Islamic Society trustee -- outspoken Egyptian Sunni cleric Sheikh Youssef al-Qaradawi -- praised Hamas and Hizbollah, which the U.S. State Department regards as terrorist organizations.

"There is a great deal of anxiety," said Larry Lowenthal, executive director of the American Jewish Committee's chapter in Boston, whose Jewish population of about 240,000 is the fifth largest of U.S. cities.

"The distance that I think has to be established between these current leaders and their colleagues who have made troubling statements ... that distance has to be clearly distinct and established," he added.

American Muslims are watching the case closely.

"Unfortunately, I see the Boston case as indicative of a growing trend in anti-Muslim rhetoric that has grown after 9/11," said Arsalan Iftikhar, legal director of the Washington-based Council on American-Islamic Relations, the nation's largest American Muslim civil rights group.

"It has especially impacted local Muslim communities in terms of building their mosques," he said. "High concentrations of Muslim populations are being given a hard time for just trying to practice their faith."

Demographers estimate there are five to six million Muslims in the United States.

DONORS FEARFUL

Growing rancor and the prospect of a high-profile court battle are frightening would-be donors and choking off funding for the mosque. Opening the red-brick building, which is now about 70 percent complete, has been delayed indefinitely.

"There is definitely fear in the fund-raising community about giving to Islamic organizations," said the Islamic Society's assistant director, Salma Kazmi.

"Everyone is worried about their name appearing on a list and whether they will get visited by the FBI," she said. "People want us to publish our donor list but if we do that we would never get any donations because everyone feels they'll be subject to all kinds of harassment."

A full-page advertisement in Boston's Jewish Advocate newspaper on Thursday accused the Islamic Society of using litigation to stifle discussion and of failing to answer questions raised by Jewish leaders who say July's bombings in London sharpened their concerns over mosques and terrorism.

One separate lawsuit brought by a city resident seeks Boston to force the Islamic Society to return the land under the mosque to the city, charging that the Boston Redevelopment Authority breached constitutional divisions between state and religion by selling the site at below-market value.

In 2000, Boston sold land at a fraction of its $400,000 value in return for a commitment to develop the site into a community center. The society says Boston has donated land to other religious institutions in the past and that the suit also reflects a concerted campaign against them.

"This is not the first time the city has given land to a religious institution but we're the only one that has been through a public hearing process," said Kazmi.

By Jason Szep