Madrid — The shipping agent for an Iranian supertanker caught in a diplomatic standoff said the vessel is ready to depart Gibraltar in "24 to 48 hours," despite a last-minute effort by the United States to seize it again.

Richard de la Rosa, managing director of Astralship, said Saturday that logistical preparations are underway and that a new crew of Indian and Ukrainian nationals is expected to take command of the ship, which is carrying 2.1 million tons of Iranian oil.

The ship was detained for over a month in Gibraltar for allegedly attempting to breach European Union sanctions on Syria.

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The U.S. obtained a warrant Friday to seize the vessel over violations of U.S. sanctions, money laundering and terrorism statutes. Calls to Gibraltar's Supreme Court and government have not been answered.

A view of the Grace 1 supertanker on August 15, 2019. Marcos Moreno / AP

Tensions concerning Iran and navigation in the Persian Gulf will be a focus for the U.N. Security Council on Tuesday, CBS News' Pamela Falk reports, when Secretary of State Mike Pompeo will address the Council and meet with the Secretary General.

Those tensions have escalated since President Trump last year unilaterally pulled the U.S. out of the 2015 nuclear deal signed by Iran and other world powers.

The decision re-imposed sanctions on Iran, stopping billions of dollars in business deals, largely halting the sale of Iran's crude oil internationally and sharply depreciating Iran's currency, the rial. More recently, the Persian Gulf has seen attacks on oil tankers and other high-stakes confrontations.