Kenya's parliament has approved the integration of government troops in Somalia into the African Union (AU) force fighting militant Islamists.
The decision comes after the AU last week asked Kenyan troops to join its 9,000-strong force in Somalia to battle al-Qaeda-linked group, al-Shabab.
The AU has about 9,000 troops in Somalia's capital, Mogadishu.
Kenya already has troops in Somalia pursuing al-Shabab which it blames for a spate of recent abductions.
Al-Shabab denies the allegation that it is behind kidnappings in Kenya and says it views the presence of Kenyan troops in southern Somalia as an act of war.
The BBC's Duncan Munene in the Kenyan capital, Nairobi, says parliament's decision shows that Kenya wants to be part of regional initiatives to tackle al-Shabab, which is linked to al-Qaeda.'Untold suffering'
The decision is probably also linked to government concerns about the rising cost of military operations in Somalia, our reporter says.
Kenya would now expect its operation to be financed by the AU or United Nations, he says.
The AU force in Somalia operates under a UN Security Council mandate.
Somalia's President Sheikh Sharif Ahmed - a moderate Islamist - initially opposed Kenya's intervention, but later supported it, correspondents say.
Last week, the AU Peace and Security Council said it had formally asked Kenya to join the AU operation in Somalia.
Kenyan military action in south-central Somalia - along with gains made by AU forces in Mogadishu - created an opportunity to end the "untold suffering" of Somalis, it said.
It also welcomed Ethiopia's decision to support the AU-Kenyan military campaign in Somalia, the council said.
Last month, Ethiopia denied that its troops had returned to Somalia - about two years after they withdrew after suffering heavy casualties.
Reports said the troops were in Somalia's Gurel town in Galgudud region and in several other areas as well.
Foreign military intervention in Somalia is intended to prevent al-Shabab from overthrowing the weak interim government.
Al-Shabab announced a "tactical withdrawal" from Mogadishu in August after fierce fighting with AU forces.
Kenyan troops have been active in parts of southern Somalia since October. Kenyan military spokesman, Maj Emmanuel Chirchir, said they intended to capture 10 towns under al-Shabab's control - including the port city of Kismayo.
Djibouti and Sierra Leone have also promised to bolster the AU force by sending around 1,500 troops each.
AU commanders in Somalia say they need about 20,000 troops to hold on to territory captured from al-Shabab.
Somalia has not had a functioning central government for more than 20 years and has been wracked by fighting between various militias.