UPDATE 2-APEC leaders back off on emissions cut target-draft

* APEC leaders choose weaker wording on emissions cuts

* Chinese say including 50 pct target might disrupt talks

* South Korea opts for toughest 2020 emission goal

* U.S., Japan agree ambitious mid-century emissions cut (Adds Chinese negotiator comments in paragraphs 3-4, 6)

By David Fogarty, Climate Change Correspondent, Asia

SINGAPORE, Nov 14 (Reuters) - Asia Pacific leaders are backing away from a target of halving greenhouse gas emissions by 2050, pledging instead to "substantially" slash them by that date, the latest draft of their summit statement says.

The Asia Pacific Economic Cooperation (APEC) meeting in Singapore is the last major gathering of global decision-makers before a U.N. climate summit in Copenhagen in three weeks meant to ramp up efforts to fight climate change.

"The 50 percent reduction did appear in the draft, but it was very controversial," said Yi Xianliang, counsellor at the department of treaty and law at the Chinese Ministry of Foreign Affairs, who is negotiating in the climate talks.

"If the reduction was in this statement, it might have disrupted negotiations," Yi told a news conference, adding the decision to remove the target was a collective decision.