Calls by Kenya’s Prime Minister Raila Odinga last week for US financial aid for a planned Kenyan assault on the Somalia port of Kismayu could go unanswered due to growing resistance in the US Congress.

A powerful American senator told The EastAfrican a few days prior to Mr Odinga’s remarks that he is seeking to cut American military aid to Kenya.

“Lack of credible investigations or punishment of those responsible” for human rights violations was cited by Senator Patrick Leahy as the reason for his move to eliminate as much as $2 million worth of US military training and equipment for Kenyan forces.

Kenya said the anticipated taking of the key seaport of Kismayu by mid August from the grip of Al Shabaab will be key to a successful shift of power from the Somali government to a civilian administration.

(Read: Haji says no to Kismayu attack without back-up)

While calling for international support, Mr Odinga said so long as Kismayu was still under the control of the Al Shabaab, the possibility of neutralising the group would remain distant because the seaport served as its economic hub.

“August will be a crucial month for Somalia owing to the fact that it will be a transitional period to an elected civilian government in Mogadishu and this will only happen when the whole of the country has been liberated,” Mr Odinga said.

Kismayu, Somalia’s third largest city, is considered the hub of the militant group, Al Shabaab, which formally merged with the dreaded global terror network, Al Qaeda, after several years of pledging loyalty and ideological similarities. “Without controlling Kismayu, it’s very difficult to completely neutralise Al Shabaab,” Mr Odinga said.

Two weeks ago, Kenyan soldiers backed by Somali forces carried out airstrikes in Kismayu in an attempt to force Al Shabaab out of the port city. The KDF is using naval warships to patrol the coast off Kismayu, targeting militant camps and bases in the economic hub.

Leahy’s initiative, which commands broad support in the US Congress, is aimed at Kenyan units involved in alleged human-rights violations at Mt Elgon in 2008, Wajir and Mandera in 2011, and in the Dadaab refugee complex late last year. Civilians were reportedly killed by Kenyan security personnel in some of the incidents referred to in Leahy’s legislation.

“Kenya and the United States have been allies for many years,” the veteran Democratic senator said, “but that does not mean we give them a blank check when it comes to US aid. ”While the sum of money targeted for potential elimination is not that large in the context of US military spending, “it does send a message,” noted a member of Leahy’s staff.

A congressional decision to cut American security assistance would hurt Kenya’s efforts to rehabilitate its reputation in the United States following the election violence in 2008. The Obama administration would also find it difficult to help finance a Kenyan attack on Kismayu if Congress were to de-fund segments of the Kenyan military on the basis of human rights abuses.

US financial support for an offensive against the Al Shabaab stronghold could be provided, however, as part of Washington’s funding for Amisom troops in Somalia. Ambassador Johnnie Carson, the top Africa official in the State Department, hinted that such an option might be under consideration.

“We are very pleased with the rehatting of the Kenyan troops in Somalia,” Mr Carson said at a news conference in Nairobi last week. He was referring to the recent absorption into Amisom of the more than 4000 Kenyan troops now inside Somalia.

(Read: UN unveils new look Amisom as Kenya joins up)

“We will continue to provide assistance to Amisom as long as al-Shabaab remains a threat to people in the region,” Carson added.

Kenya can, in any event, avert the threatened cutoff of US military financing by satisfying the State Department that it is responding appropriately to the alleged abuses cited in Leahy’s legislation.