"If Iran thinks it can use this time to build more leverage and then come back and say they want something better it simply won't work. We and our partners won't go for it," Malley told BBC Sounds, as quoted by Reuters.
"If that's Iran's approach, which is to try to use the negotiations as cover for an accelerated nuclear program, and as I say, drag its feet at the nuclear table, we will have to respond in a way that is not our preference," added Malley. "Nobody should be surprised if at that point there is increased pressure on Iran."
"We hope not to get that there, but if we are, then pressure will have to increase to send a message to Iran that the choice it is making is the wrong one. That it has a different path available to it, but it's not a path open indefinitely because Iran's nuclear program is putting the very essence of the deal negotiated (in 2015) at risk," he stressed.
Iran has gradually scaled back its compliance with the 2015 nuclear deal it signed with world powers in response to former US President Donald Trump’s withdrawal from the agreement in May of 2018.
On Monday, indirect talks between the US and Iran on return to compliance with the nuclear deal are scheduled to resume in Vienna.
Iran has repeatedly demanded that the US lift sanctions imposed on Iran as part of the nuclear talks and also reassure Iran it will not abandon the deal again.
US officials have said that while they prefer the diplomatic route to reach an agreement with Iran, there are other options on the table should that fail.
Malley said earlier this week that Washington will not "sit idly" on Iran if it drags its feet on returning to the nuclear deal.
Meanwhile, General Kenneth McKenzie, the top US commander in the Middle East, said that Iran is “very close” to a nuclear bomb and his forces stand ready with a potential military option should talks with the Islamic Republic fail.
