The United States is urging allies and companies to stop buying crude oil from Iran by Nov. 4 or they will face sanctions, a State Department official told reporters on Tuesday.

The official indicated that there would be no additional phase-out period after the sanctions kick in at the end of the 180 days from when President Donald Trump unilaterally withdrew from the Iran nuclear deal in May. Also, there will likely be no waivers. The Treasury Department said that same day that U.S. sanctions on Iran would take effect in 90-day and 180-day periods - after Aug. 6 and Nov. 4.

The official also said the U.S. is holding talks with Turkey, China and India, which all import oil from Iran. To skirt sanctions countries can try to do deals that avoid using U.S. dollars.

The U.S. is pursuing what it describes as a maximum pressure campaign against Iran.

U.S. allies in Europe are, however, upset Washington withdrew from the deal, negotiated under Trump's predecessor Barack Obama, saying it was achieving its goal of preventing Tehran from obtaining nuclear weapons.

The move will likely add pressure to rising oil prices, even as U.S. ally Saudi Arabia - a regional rival of Iran - indicated it will increase output. Russia has also signaled it plans to raise production levels. Iran's crude production was around 3.8 million barrels per day in May, according to OPEC's Oil Market Report for May. The country exports more than 2 million barrels of oil.

Iran is deeply involved in Syria, for example, and also supports militant groups elsewhere, including in Yemen. Tehran's regional activity is a source of concern for Saudi Arabia and the US administration, with Washington arguing the nuclear deal freed up Iran to engage with more projects outside its borders.