The top U.N. envoy in Afghanistan says the country's national unity government must overcome five hurdles in 2016 to survive.

Nicholas Haysom told the U.N. Security Council on Tuesday that "survival cannot mean inaction, or merely 'treading water.'"

Haysom says the government must tackle a contracting economy with low growth and high unemployment, an intensifying insurgency and "an increasingly fractious and divided political environment."

He says it must also secure significant international financial support and make "progress towards a sustainable peace, without which all the other gains will be threatened."

Haysom also forecasts "a difficult fighting season" ahead. An emboldened Taliban has continued to test Afghan forces since the U.S. and NATO formally concluded their combat mission in the country at the end of 2014.