People in the US who quietly band together and adopt radical ways, not just established overseas terrorist groups like al-Qaida, pose a serious threat to the American's security, a new police analysis has concluded. The New York Police Department report, to be released Wednesday, describes a process in which young Muslim immigrants, frustrated with their lives in their adopted country, slowly adopt a philosophy that puts them on the path to jihad. The men meet and share ideas in mosques, in bookstores and over the Internet, it says. Police officials say the report warns that potential terrorists are difficult for law enforcement to detect because they blend in well. It also argues that more intelligence gathering is needed to thwart terror plots at their earliest stages.