The United States will on Thursday recognize the first Somali government in two decades, heralding a significant shift in ties since the deadly 1993 attack on U.S. helicopters over Mogadishu.

The beginning of the new chapter will come when U.S. Secretary of State Hillary Clinton exchanges diplomatic notes with visiting Somali President Hassan Sheikh Mohamud, a top U.S. official said Wednesday.

"The visit here this week of the new Somalian president Hassan Sheikh Mohamud represents a significant change in the security and political situation on the ground in Somalia and our relationship with that country," Assistant Secretary of State Johnnie Carson told journalists.

It will be Clinton's first meeting with the new Somali leader who was only elected in September, and was relatively unknown outside his country.

Somalia has not had an effective central government since 1991. Two years later, Americans were shocked by scenes of U.S. soldiers being dragged through the streets of Mogadishu after Somali militants shot down two Black Hawk helicopters. Eighteen Americans died, and 80 were wounded.

However, a new Somali administration took office last year, ending eight years of transitional rule by a corruption-riddled government.

And in recent months, a 17,000-strong African Union force, fighting alongside government troops and Ethiopian soldiers, finally wrested a string of key towns from the control of Islamist Shebab insurgents.

Carson hailed recent U.S. policies on Somalia, and praised the work of African nations through the African Union force in Somalia AMISOM, which helped oust the militants from their last major stronghold of Kismayo in September.

"This has been a major, major success. We are long way from where we were on October 3, 1993 when Black Hawk down occurred in Mogadishu," Carson said.

"Significant progress has been made in stabilizing the country and in helping to break-up and defeat al-Shebab. Much more needs to be done but we think enormous progress has been made," he added.

Carson has repeatedly stressed that the success in Somalia should be seen as a model for African-led peacekeeping forces in the region.

A university lecturer, Hassan Sheikh Mohamud defied predictions and was chosen by lawmakers as Somalia's new president from among a dozen hopefuls in September elections.

Clinton swiftly congratulated him on his win, which was hailed by the U.S. administration as "an important milestone" for the country.

His party described the new president as the architect of Somali civil society, and unlike many Somali politicians he is not part of the diaspora.

But he inherits an ongoing war, a humanitarian crisis, feeble institutions and deeply entrenched warlordism. Al-Qaeda-linked Shebab rebels, who still control vast swathes of the country, dismissed his election as illegitimate.

The U.S. move on Thursday will open doors to the country, which will also be the focus of a new international conference to be hosted in Britain in May.

"This will build on last year's successful meeting in London to help sustain international support for the progress being made by the Somali government," a spokeswoman for the office of British Prime Minister David Cameron said.

A U.S. official, who asked to remain anonymous, said no official American aid package would be unveiled at the State Department meeting on Thursday.

However "the fact that we recognize a government there would allow us to do things through USAID we have not been able to do before," he said.

"The fact that we recognize them as the legitimate government would allow the World Bank and the IMF to do things that they had not been able to to before." (AFP)