The administration of US President Barack Obama began the long process of briefing the US Congress on Friday about a new arms sales package for Taiwan that does not include desperately needed F-16C/Ds, sources said.

It is not clear exactly what is included — one source said it amounted to US$4.2 billion worth of materiel — but almost certainly does contain upgrades for the existing fleet of aging F-16A/Bs.

No official announcement has been made, but the full arms package is likely to become public next week when the White House formally sends it to Capitol Hill.