A senior operative of the al-Qaida network in Yemen — the group that claimed responsibility for the failed Christmas Day attack on an American passenger jet over Detroit — has threatened more attacks on the United States.

The US has become increasingly worried about militants based in Yemen since al-Qaida groups there and in Saudi Arabia merged last year to become al-Qaida in the Arabian. The group has openly targeted US and other Western interests in Yemen, and — as demonstrated by the Dec. 25 attack — abroad.

Qasim al-Raimi, a top military commander for al-Qaida in the Arabian Peninsula, warned Americans in an article published in an online militant magazine that the group "will blow up the earth from below your feet."

"You have attacked us in the midst of our household, so wait for what will attack you in the midst of yours," al-Raimi said, according to a translation of the message from the SITE Intelligence Group, which monitors militant Web sites.

The United States is increasingly worried that Yemen is becoming a significant terrorist staging ground, amid signs that lower-level al-Qaida operatives have been moving into the country from the Afghanistan-Pakistan border region.

Washington has pressured Yemen's government to crack down on the network, and the Pentagon has earmarked some $150 million in military assistance to Yemen to help combat the threat.

Al-Raimi claimed in the article that US efforts have backfired, and only succeded in pushing more Yemenis into the militant fold. "You united us with our people, made our catastrophe one," he said.

Al-Raimi is one of 23 militants who broke out of a prison in San'a in February 2006 and is at large. Yemeni authorities have said they believe he was involved in the July 2007 suicide bombing that killed eight Spanish tourists and two Yemenis visiting a temple in central Yemen.

He escaped a Yemeni military strike in December 2009 that killed a deputy commander and at least 30 other suspected militants.

Worries over al-Qaida in the Arabian Peninsula's growing presence are compounded by fears that Yemen could collapse into turmoil from its multiple conflicts and increasing poverty and become another Afghanistan, giving the militants even freer rein.