UPDATE 4-South Sudanese register for independence vote

* North, south leaders agree "soft border" in framework

* Ownership of Abyei oil region still to be resolved - AU

* Thousands queue to register in south; north subdued (Adds White House comment)

By Jeremy Clarke and Opheera McDoom

JUBA/KHARTOUM, Nov 15 (Reuters) - Thousands of south Sudanese started registering for their long-awaited independence referendum on Monday, their first concrete step toward a vote that could split Africa's largest country in two.

The launch came after northern and southern leaders agreed they would form a "soft border" allowing the free movement of trade and nomads between their territories in the event of separation, as part of a framework agreement to resolve a list of disputes between the two sides.

The referendum on whether the oil-producing region should declare independence, scheduled for Jan. 9, is the climax of a 2005 peace deal that ended decades of north-south conflict -- Africa's longest civil war that was fought over ethnicity, religion, ideology and oil and that killed 2 million people.

Analysts widely expect southerners embittered by the long war to vote for secession.

Southern President Salva Kiir, surrounded by chanting crowds and drummers in the southern capital of Juba, was among the first to sign up for the vote, a Reuters witness said.