US Vice President Joe Biden opened a high-profile meeting on global extremism Tuesday by facing down critics who say the White House should focus on defeating it militarily. The summit hosted by President Barack Obama has been in the pipeline for months but has been given deeper significance after several similarly inspired attacks, including on a cultural center and on a synagogue in Copenhagen which left two people dead at the weekend. The White House has been criticized for **t specifically focusing the three-day meeting on combating Islamic extremism or broader military efforts to tackle jihadist groups such as Islamic State. On Sunday, a video emerged apparently showing Islamic State jihadists beheading 21 Egyptian Christians in Libya.