Kenyan forces that invaded neighboring Somalia Oct. 16 are advancing toward an expected showdown with Islamist fighters of al-Shabaab, which has links to al-Qaida, around the town of Afmadow, key to the insurgents' supply lines.

There are indications that the United States and France are aiding the Kenyan operation, although that could be a risky enterprise.

The Americans were the prime movers behind an Ethiopian invasion in 2006 to oust an Islamic regime in Mogadishu. It succeeded but gave rise to al-Shabaab, which until recently held way over most of the country.

The Kenyan force appears to have made significant gains in its two-pronged offensive, which is aimed at seizing the al-Shabaab stronghold of Kismayo, a strategically important port city on Somalia's Indian Ocean coast about 55 miles south of Afmadow.

One column is moving east from the Kenya border while another is looping around to the south after capturing the coastal town of Oddo Oct. 21.

The Kenyans launched the operation with two battalions totaling 1,600 troops. They're now estimated to number around 4,000 regular troops, supported by several thousand allied Somali militiamen.

Kenyan air force F-5 jets have carried out several airstrikes on al-Shabaab positions and bases across southern Somalia.

The Kenyans thrust into Somalia after a rash of kidnappings by al-Shabaab and signs that the anarchy in Somalia that has gripped the Horn of Africa country for two decades was about to spill over into the East African state.

Kenya is a key supporter of the Western-backed Transitional Federal Government in Mogadishu, Somalia's capital, which was installed with U.S. help in December 2006 after a short-lived Islamist regime had been dislodged.

The objective of the new invasion appeared to be setting up a buffer zone along the Kenyan border with pro-Kenyan militias to block al-Shabaab.

However, the U.S. global security consultancy Stratfor observed: "At this point, Kenya's ultimate aims and intentions remain opaque.

"Kenyan forces certainly have the capability to continue conducting operations but the number of Kenyan forces currently deployed is insufficient to completely eradicate al-Shabaab or even secure the areas they have seized thus far."

The French air force is providing logistical support, flying in troops and supplies from Nairobi to an airfield close to the Somali border.

The French recently stepped up operations against al-Qaida in North Africa after French citizens were kidnapped by the jihadists. Al-Shabaab has held a French citizen hostage for two years, which could explain French support for the Kenyan operation.

A Kenyan military spokesman said Oct. 24 the French navy had shelled insurgent positions in Koday, on the coast between Oddo and Kismayo, but Col. Thierry Burkhard, a French military spokesman, denied that.

Last week al-Shabaab was driven out of the coastal town of Ras Kamboni, south of Oddo, by Somali militiamen allied to the Kenyans and shelling by the Kenyan navy.

The Americans, who have mounted several air and missile strikes against al-Shabaab's leadership over the last three years, say they aren't involved.

But the Kenyan media has reported that U.S. unmanned aerial vehicles have carried out several airstrikes near the town of Bur Gavo, south of Koday and on the expected line of march of the southern Kenyan column.

The Americans, like the French, have an interest in helping the Kenyans hammer al-Shabaab.

The CIA has used the U.S. military's counterinsurgency base in the former French colony of Djibouti, Somalia's northern neighbor, to launch UAV strikes against Islamist fighters in Somalia and Yemen, across the Gulf of Aden.

The Americans claim al-Qaida in the Arabian Peninsula is seeking to persuade al-Shabaab to join it to mount attacks on the United States and threaten oil supply lines from the Persian Gulf.

The CIA and the U.S. Joint Special Operations Command have recently intensified covert operations against both AQAP and al-Shabaab.

The Kenyan incursion undoubtedly supports that campaign by putting pressure on al-Shabaab and flushing out its leadership cadres who are the Americans' primary targets.

Meantime, the Kenyan advance seems to be slowing, apparently because of heavy rains as the monsoon season begins.

But al-Shabaab is reported to be digging in around Afmadow, indicating it plans to make a stand there to halt the Kenyan advance.