The price of Brent crude oil could jump as high as $US100 a barrel next year as sanctions on Iran shrink inventories, analysts warn.

Bank of America Merril Lynch analysts said the Brent crude price was likely to reach $US90 by mid-2019. If OPEC and Russia kept in place their existing oil production cuts for 2018 and beyond, the price could even rise to $US100 before the end of next year, they said.

President Donald Trump shows a signed memorandum confirming the US withdrawal from the Iran nuclear deal. Credit:AP

"We introduce a second-quarter $US90 a barrel Brent price target for 2019 and see a risk of $US100 a barrel oil next year, although we are concerned that these market dynamics could unfold over a shorter timeframe," BoA strategist Franciso Blanch said.

It follows a decision by US President Donald Trump to dump a nuclear agreement with Iran and reinstate “the highest level of economic sanctions” on Iranian oil, potentially pulling almost 1 million barrels of oil a day from the global market.