Man holed up in Sydney house after threat

Police have surrounded a home in Sydney's west where a man is believed to be holed up after threatening government employees.

Police were called to Chopin St in Seven Hills about 10.30am on Thursday after a man allegedly threatened Department of Housing staff and claimed he was armed with a weapon, police told AAP.

When officers arrived, the man allegedly refused to let them in. Negotiators are attempting to speak with the man.