United Nations Secretary General Ban Ki-moon says international peacekeepers have helped Somalia's government make major security gains in the capital, Mogadishu, but he says they need additional reinforcements to stabilize the rest of the country.

Mr. Ban made the remarks Tuesday after a brief visit to Somalia, the first by a U.N. chief in more than 18 years.

He said his visit was a sign of the improved security situation, which he said will also enable the U.N. Political Office for Somalia to relocate to Mogadishu next month.

But Mr. Ban said in order to press the momentum beyond the capital, the African Union peacekeeping force, known as AMISOM, must deploy at its full strength of 12,000 troops. He also said the U.N. was studying whether the mandate ought to be increased even further.

The U.N. Security Council said in a statement Tuesday it recognized Somalia's need for international support to continue its progress.

But the statement said future support of the TFG will be contingent on its completing by August 2012 key tasks laid out in the so-called “Roadmap” leading toward new elections and reforming its parliament and constitution.

The Transitional Federal Government currently controls Mogadishu supported by some 9,000 A.U. troops from Uganda and Burundi and additional troops from Kenya and Ethiopia.

Last month, African Union diplomats discussed asking for U.N. authorization to double the size of the AMISOM force to 20,000 troops.

Somalia has endured 20 years of lawlessness and conflict since the fall of the last stable government.

Al-Shabab, which controls most of central and southern Somalia, has waged a four-year campaign against Somalia's government in an attempt to impose strict Islamic law.