US President Donald Trump has suggested that former Secretary of State John Kerry has provided Iran with “very bad advice” and may have violated US law by advising the Islamic Republic.

Axar.az reports citing PressTV.

“Iran is being given VERY BAD advice by John Kerry and people who helped him lead the US into the very bad Iran Nuclear Deal,” Trump wrote on Twitter on Monday.

"Big violation of Logan Act?” Trump asked.

In May last year, Trump pulled the US out of the Iran nuclear deal, known as the Joint Comprehensive Plan of Action (JCPOA), claiming that it was a bad deal.

Kerry, who served during the administration of former US President Barack Obama, has criticized the Trump administration for pulling out of the accord.

Kerry, who played a main role in the nuclear talks, has described it as the “single strongest, single most accountable, single most transparent nuclear agreement anywhere in the world.”

Since leaving his post, Kerry has had several talks with the Iranian side, advising them to wait out until Trump leaves the office.

Trump made a similar attack against Kerry last year, saying he made “illegal meetings” with Iranian officials.

Kerry’s efforts may be in violation of the Logan Act, a US law enacted in 1799, which criminalizes unauthorized negotiations with foreign governments having a dispute with the United States. Only two people have been indicted for violating the act in 1802 and 1852.

Some US media outlets and opponents of the Trump administration accused then-National Security Adviser Michael Flynn of violating the Logan Act, claiming he was not authorized to speak with Russian Ambassador Sergey Kislyak before the inauguration.

Trump brought up Kerry’s potential violation after the White House announced that all importers of Iranian oil will have to end their imports shortly or face US sanctions.

Last November, the US enforced sanctions targeting the Islamic Republic’s banking and energy sector, however, it granted waivers from the bans to eight major importers of the Iranian oil, fearing market instability including China, India, Japan, South Korea, Taiwan, Turkey, Italy and Greece.