Standard Chartered remains under U.S. supervision six years after accusations it breached Iran sanctions, but Chief Financial Officer Andy Halford told CNBC that the bank is making "good progress."

In 2012, the New York State Department said the British lender hid $250 billion worth of transactions with the Iranian government. Following an agreement in the same year, where it reached a $340 million settlement, it has been under the care of an independent monitor to improve its money laundering prevention scheme.

Halford told CNBC's "Street Signs" Wednesday that Standard Chartered is still being observed.

"We have got monitors in, we are making good progress, but these are very, very complex issues," Halford said.

"We are dealing in many, many countries around the world … We have been noticed by the monitors (as) having made very good progress, it's just we are not quite across the line yet."

The agreement to remain under supervision has been extended twice and is currently due to expire in July.