which 用法

which 用法
North Korea announced Thursday that it will launch its newest rocket,which many outside the country suspect is a long-range missile that can hit the U.S.mainland,sometime from April 4 to 8,giving other countries three weeks to decide whether to shoot it down or deal with the trouble in another way.
中的
which many outside the country suspect is a long-range missile that can hit the U.S.mainland,
单看这个句子中的which many outside the country suspect 好像是作主语从句
而语法上没有查到which加一个句子作主语的用法这里怎么解释?
我就是想问{which many outside the country suspect is a long-range missile that can hit the U.S.mainland,} 这个定语从句再进一步划分句子成分怎么划？