LONDON, United Kingdom - A fourth round of nuclear talks between Tehran and Washington has been postponed, Iran's Foreign Ministry declared in a statement published by state media on Thursday. 

The meeting had been initially scheduled to take place in Rome on Saturday. 

Foreign Ministry spokesman Esmail Baghaei said in the statement that "a possible new date" will be announced in due course. 

He did not elaborate on what prompted the postponement, only noting that it was "suggested" by the Omani government, which has been mediating the US-Iran diplomatic initiative in three meetings since mid-April. 

Baghaei reaffirmed the Iranian delegation's "goodwill" and "manifest frameworks" to seek the lifting of "unlawful sanctions." He added that Iran has been aiming for a reasonable, fair, and lasting agreement that safeguards the well-being of its citizens.

In the first three rounds, the US side has been seeking assurances that Tehran will not acquire nuclear bombs, as the Islamic Republic demands full sanctions relief in any final accord. 

Earlier in the day, the spokesperson released a separate statement condemning as "hostile and inhumane" a set of new US sanctions slapped on Iran's oil industry. Baghaei asserted that the move undermines the current diplomatic process. 

He warned that the US government would bear full responsibility for the consequences of its "provocative" and "contradictory" behavior toward the Islamic Republic, stressing that such measures deepen Iranian mistrust.

The US State Department announced the sanctions on Wednesday, targeting seven entities based in the UAE, Turkey, and Iran, accusing them of aiding Tehran's sale of its crude and petrochemical products.

"So long as Iran attempts to generate oil and petrochemical revenues to fund its destabilizing activities, and support its terrorist activities and proxies, the United States will take steps to hold both Iran and all its partners engaged in sanctions evasion accountable," read the statement issued by Secretary of State Marco Rubio.

The new sanctions fall within President Donald Trump's "maximum pressure" policy, designed to squeeze Iran's oil revenue, a key lifeline for its battered economy.