US President Donald Trump announced on Monday that his country is imposing new and "hard-hitting" sanctions on Iran amid high tensions between Washington and Tehran.

Trump signed an executive order at the White House on Monday, slapping additional economic sanctions on Iran. Trump told reporters that the targets of the new sanctions include Iran's Supreme Leader Ayatollah Ali Khamenei.

The new action is "imposing hard-hitting sanctions on the Supreme Leader of Iran and the office of the Supreme Leader of Iran and many others," said Trump.

He alleged that the supreme leader "ultimately is responsible for the hostile conduct of the regime."

The sanctions imposed by the order will deny Iran's leadership access to financial resources, blocking them from using the US financial system or accessing any assets in the United States.

Trump said Monday's move came after "a series of aggressive behaviors by the Iranian regime in recent weeks" including shooting down a US drone, which he described as "not good and not appropriate."

US Treasury Secretary Steven Mnuchin revealed in a following press conference that the new executive order will freeze billions of additional dollars in Iranian assets.

Mnuchin also said Trump has instructed him to designate Iranian Foreign Minister Mohammad Javad Zarif "later this week."

The newly signed executive order has allowed Mnuchin to impose sanctions on officials appointed to their position by the Iran's supreme leader.

Also on Monday, US Treasury announced that it has blacklisted eight senior commanders of Navy, Aerospace, and Ground Forces of the Iranian Islamic Revolutionary Guard Corps (IRGC), citing their supervision over the IRGC's "malicious regional activities."

As a result of today's action, all property and interests in property of those individuals that are in the United States or in the possession or control of US persons must be blocked, said the Treasury in a statement.

While intensifying the economic pressure on Iran, Trump avoided further stoking the already tense military tension in the region.

"We do not seek conflict with Iran or any other country," he said on Monday, adding that he looks forward to "discussing whatever I have to discuss with anybody that wants to speak."

Zarif, in response to the US new sanctions, said in a tweet that the hawkish senior US officials close to Trump "despise diplomacy, and thirst for war."

Tensions remain high in the region over Iran's downing of a US military drone last week and Trump's decision to abort imminent military strikes against Iran in retaliation.

Over the past month, Washington has beefed up its military forces in the Middle East, which Iran described as a disturbing element.

Iranian President Hassan Rouhani said on Sunday that military intervention of the United States in the region has caused problems for the nations, semi-official Fars news agency reported.

Ties between the United States and Iran have deteriorated significantly after Washington walked away from the landmark 2015 Iran nuclear deal in May 2018 and reimposed energy and financial sanctions, which had been removed under the deal, on Iran.

Iran has suspended parts of its commitments subject to the nuclear deal and have threatened to go further.