US President Donald Trump has signed into law a Russia sanctions bill that gives his administration the authority to impose tariffs of up to 100 per cent on imports from countries that buy Russian oil and gas, potentially exposing India and China to steep US duties.

The legislation requires tariffs of up to 100 per cent to be imposed within 30 days on goods from the five largest importers of Russian crude oil or gas, although it does not name the countries or specify how the top-five list will be determined.

The legislation also applies to countries that knowingly make new purchases of Russian oil or gas after the law takes effect, as well as the five countries deemed to be providing the most assistance to Russia in evading sanctions.

India and China are among the biggest buyers of Russian oil. However, the law does not specifically name either country, leaving the Trump administration considerable discretion over which countries could ultimately face tariffs.

The measure also targets Russia’s so-called shadow fleet of oil tankers, which has been accused of helping Moscow evade sanctions. It further gives Trump the authority to waive tariffs or sanctions on national security grounds.

The bill, which targets Russia’s energy and defence sectors, was passed by the US House of Representatives on Wednesday before Trump signed it on Friday. The Senate had previously approved the legislation.

The legislation comes after more than a year of delays. Trump agreed in July to move the bill forward. According to the report, some US officials had pushed for its passage ahead of a planned meeting between Trump and Chinese President Xi Jinping next week, seeking to give the president additional leverage.

White House legal director James Braid said the legislation was the first in nearly 40 years to give Congress new tariff powers to the executive branch.

Concerns have been raised over the legislation because it does not clearly identify which countries could ultimately face tariffs. Janet Chu, vice-president of the National Foreign Trade Council, said various calculations were being discussed about which countries could be affected, including India, Brazil, Japan and some European Union countries.

India has warned that new US tariffs could affect bilateral relations, while China has opposed what it described as “far-reaching jurisdiction” without a basis in international law.

Critics of the legislation have also argued that its language is too broad and gives the president excessive authority. Lawyer Laura Brank said the wide powers granted to the president could create scope for their misuse.

The Foundation for Defense of Democracies, however, said the bill contained sufficient criteria for determining which countries could face measures and did not provide a hidden opportunity to impose tariffs on unrelated products.

The timing of any new tariffs could also have economic and political implications. The law requires tariffs to be announced within 30 days. Analysts cited by Reuters said Trump could be reluctant to take measures that might raise consumer prices and energy costs, particularly ahead of the November midterm elections.