About 750 to 1,000 foreign fighters, including American citizens, are now swelling the ranks of Al Qaeda’s affiliate in Somalia, a senior Kenyan military official tells Fox News.

The group, known as Al-Shabaab, has taken advantage of the Arab Spring to further cement its relationship with the Al Qaeda affiliate in Yemen, the Kenyan military official added.

Amplifying the point, Macharia Kamau, Kenya’s ambassador and permanent representative to the Kenya Mission at the United Nations, said that the two Al Qaeda affiliates appear to be on the verge of a fully integrated operation.

“We have the bodies to prove it in Mogadishu (the Somali Capital),” Kamau told Fox News, referring to the suicide car bombings. “Unquestionably, the training capabilities are international and the funding behind these training capabilities are international.”

Fox News has learned that in addition to training recruits in Somalia, Al Qaeda in Yemen, which is behind the last two major plots against the U.S. involving aircraft, has begun sharing bomb-making techniques with Al-Shabaab.

This is significant because the Yemeni Al Qaeda affiliate's Saudi bomb maker, Ibrahim al-Asiri, is considered a top target by U.S. intelligence because he has developed explosives that defy traditional airline security screening. Al-Asiri was behind the underwear bomb in 2009 and the cargo printer bombs last fall that were designed to bring down cargo planes over the eastern seaboard of the U.S.

Kamau said there was no convincing evidence that efforts to deter U.S. citizens from joining Al Shabaab have been successful. At least two dozen Americans, mostly of Somali descent, have joined Al-Shabaab since 2007. An Alabama native, Omar Hammami, who is under indictment in the U.S. for allegedly supporting Al Qaeda, is the public face of Al-Shabaab for the West through online videos and lectures.

Kenyan officials say the presence of Americans on the ground in Somalia is making conditions worse. There are now at least three documented cases of American suicide bombers in Somalia, and a fourth case is suspected. A month ago, Kenya began an aggressive military push into Somalia to contain Al-Shabaab.

“American citizens makes the situation even more complex because you are bringing a level of competence and training that normally is not found in some of these small communities in some of these failed states," Kamau said.

As for the number of foreign jihadists and the threat they present, Kamau added, “It has definitely not reduced ... the actual suicide bombers are sometimes from America or from Sweden ... where they have some of these tentacles linking back to it.”

Kenya officials say that almost a third of the council that runs Al-Shabaab is “tied up with Al Qaeda elements,” adding that “the leadership, the strategic thinking ... and the funding is tied up in the same Al Qaeda elements that are spread in many other parts of the world," including Yemen and potentially as far afield as Afghanistan.

A strategic priority is the Somali port city of Kismayo, which is seen as the main supply route for Al-Shabaab and other extremists elements in the Horn of Africa. The Kenyan ambassador said his country wants to see a naval blockade which will require international help. And while grateful for American support, given the current economic climate, Kamau said other nations whose strategic national security interests are at stake in the Horn of Africa should also bear the responsibility.

Asked if Somalia is on the verge of becoming an Al Qaeda safe haven from which it will try to launch global operations, the ambassador said, “Without a doubt. Absolutely. The evidence of that is clear. I’m sure your own intelligence agencies (U.S. intelligence services) here are aware of it. We (the Kenyans) are aware of it. ... The countries that surround Somalia are aware of it. We are all trying to respond appropriately.”

While U.S. officials put the number of foreign fighters in Somalia at about 500 and slightly more in Yemen, they do not dispute that both affiliates are on the upswing when compared to Al Qaeda core in Pakistan that has only “several hundred” fighters.

“While Al Qaeda’s core in Pakistan is weaker now than it ever has been, the initiative in the organization and attention of foreign fighters is shifting to their affiliates in Yemen and the Horn of Africa," a U.S. official told Fox News. Al Qaeda in Yemen and Al-Shabaab “are threats no one is taking lightly.”

While Al-Shabaab has launched attacks outside of Somalia in Kenya and Uganda, the intelligence community questions whether the group will remain a regional player or whether it will truly go global by launching international plots. Al-Shabaab has not so far. One lingering concern is that Americans, with clean passports and clean backgrounds, who train with Al-Shabaab can eventually return to the U.S.

Asked whether it is only a matter of time before Al-Shabaab becomes a global player for Al Qaeda, Kenya’s U.N. ambassador framed his response carefully.

“The next 12 months are critical, “ Kamau said. “It depends how successful we are on the ground. And what support we get from the international community. If we are successful, then we should hope that we should succeed and that should not happen. And if we fail, on the other hand, which we hope we don’t, it is hard to tell what the repercussions will be for everyone.”

Fox News chief intelligence correspondent Catherine Herridge's bestselling book "The Next Wave: On the Hunt for al Qaeda's American Recruits," published by Crown, draws on her reporting for Fox News into Al-Shabaab, the American cleric Al-Awlaki and his new generation of recruits -- Al Qaeda 2.0.