UPDATE 1-U.S., UK and Norway urge South Sudan to meet deadline for transitional government

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LONDON, Oct 21 (Reuters) - The United States, the United Kingdom and Norway urged political parties in South Sudan to meet a Nov. 12 deadline to form a transitional government.

South Sudan’s main opposition leader told a visiting United Nations Security Council delegation on Sunday that he will not be part of a unity government next month, dashing the prospects of progress in a stalled peace process.

Former rebel leader Riek Machar said the parties have failed to agree on ways to integrate the army, a key condition of a peace accord signed last year, and could not see how they could form a government without it.

"South Sudan faces a critical moment in the journey toward a peaceful and prosperous future. There are now less than four weeks for political leaders to form a transitional government," the countries said in a joint statement.

"We urge the South Sudanese parties to meet the November 12 deadline to form a transitional government that will enable the conditions for a constructive relationship during the next phase of South Sudan’s peace process."

(Reporting by Guy Faulconbridge; editing by Andrew MacAskill)