Number of centrifuges, main contentious point in West-Iran nuclear talks

Just less than 48 hours of November 24 deadline, Iran and the Group of P5+1 are grappling to resolve contentious points to reach an historic deal to close the Iranian nuclear dossier. According to participants in the marathon talks, there are still many unresolved points between the two sides.
One of the major contentious points in the negotiations is the number of centrifuges that Iran nuclear facilities should have.
Iran currently has over 19,000 centrifuges and 10,000 are in the pipeline. The US seeks to reduce the number down to 4,500 centrifuges to prevent Tehran from having the ability to produce highly enriched uranium. Earlier, Iranian Foreign Minister Mohammed Javad Zarif briefed Austrian counterpart about the development of the negotiations. US Secretary John Kerry stated that meeting German Foreign Minister Frank-Walter Steinmeier that there were still "serious gaps" in the nuclear negotiations.
British Foreign Secretary Philip Hammond said there was still a "very significant gap" and raised the possibility of an extension to the deadline. The five permanent members of the UN Security Council plus Germany (the P5+1) want Iran to scale down its nuclear activities. In return Tehran, which denies seeking to develop nuclear weapons, wants the lifting of UN and Western sanctions that are causing its economy major problems.
In July after months of intense talks, negotiators gave themselves four more months, until November 24, to strike a deal. Now there is speculation about a fresh extension.