Seeking to step up pressure to force Iran to stop seeking nuclear weapons, U.S. President Barack Obama authorized on Monday to impose new sanctions targeting the Islamic republic's energy sector for the first time, saying the nation has chosen the path of "international isolation."

Obama signed an executive order authorizing sanctions on individuals who knowingly help Iran in its development of petroleum resources and the production of petrochemical products.

"New sanctions target for the first time Iran's petrochemical sector, prohibiting the provision of goods, services and technology to this sector and authorizing penalties against any person or entity that engages in such activity," he said in a statement, noting the moves "expand energy sanctions, making it more difficult for Iran to operate, maintain and modernize its oil and gas sector."

"As long as Iran continues down this dangerous path, the United States will continue to find ways, both in concert with our partners and through our own actions to isolate and increase the pressure upon the Iranian regime," he added.

In addition, the United States warned of the threats to governments or financial institutions that do business with Iranian banks, but stopped short of imposing sanctions on the banking sector in the Islamic republic.

Obama said it is the first time that the U.S. has ever identified the entire Iranian banking sector as a threat.

The UN Security Council imposed four rounds of sanctions on Iran, a major oil producer, between 2006 and 2010 as the country refused to halt its nuclear enrichment program, which Western countries suspect could be used to develop fuel for nuclear bombs.

In addition to the UN sanctions that commit all its member states, the United States and European Union have imposed extra sanctions of their own. However, Iran's oil sector had remained the key sector spared from the draconian measures over the years.

The new U.S. moves came in response to a report released on Nov. 8 by the International Atomic Energy Agency, which outlined alleged activities pointing to clandestine nuclear bombs making by Iran.

Besides, U.S. authorities alleged last month that Iran was behind a plot to assassinate the Saudi ambassador to Washington.

Britain said early Monday that it was cutting links with Iran's banks, and Canada was expected to move in a coordinated manner.