US National Security Advisor John Bolton vowed Tuesday to "squeeze" Iran "until the pips squeak", a week after a tough new round of sanctions came into force, compelling Tehran to find ways to evade the restrictions in oil trade and banking.
Speaking in Singapore ahead of a summit, Bolton said: "We think the (Iranian) government is under real pressure and it's our intention to squeeze them very hard.
"As the British say, squeeze them until the pips squeak.
"We are also going to significantly increase the enforcement of sanctions."
President Donald Trump has dramatically increased pressure on Tehran, withdrawing from the 2015 international deal aimed at ending its nuclear program and introducing several rounds of unilateral US sanctions.
The latest tranche of measures have been touted as the toughest yet, and aim to significantly reduce Iran's vital oil exports and cut off its banks from international finance.
"There's no doubt Iran has already started to try and find ways to evade the sanctions both on oil in particular and financial markets," Bolton added.
Bolton stressed that "most of the countries of Europe have passed through denial and anger and many of them are already at acceptance that we're out of the deal."
"Others are getting to that point," he said.
In the face of widespread opposition to the sanctions, Washington issued temporary exemptions to eight countries to its ban on buying oil from Iran.
Iranian President Hassan Rouhani has said that Washington would not be able to cut Iran's oil exports to zero.
