India has begun work on deploying the Russia-made S-400 Triumf advanced surface-to-air missile defense system, with the first unit to be made operational in April, local media reported Monday.

All five units will be deployed to tackle the threat from China, The Hindustan Times reported.

The two countries have been locked in an intense standoff for the past two years along the Line of Actual Control (LAC), the de facto border between China and India in the territory of Ladakh in the disputed Himalayan region of Jammu and Kashmir. Tensions soared in June 2020 after at least 20 Indian and four Chinese soldiers were killed in a border clash in the region.

Though the situation calmed after several rounds of talks, the two sides are yet to reach a resolution and have increased military deployments along the border.

All five units of the S-400 system, which can take down a hostile aircraft or missile at a range between 40 and 400 kilometers (25 miles and 248 miles), are expected to be operational by next year, The Hindustan Times quoted local officials as saying.

Specter of U.S. sanctions

In 2018, India and Russia signed a $5.5 billion contract for the S-400 system, putting India at risk of sanctions by the United States.

The U.S. has long tried to deter countries from buying military equipment from Russia, threatening them with punitive measures under the Countering America’s Adversaries Through Sanctions Act (CAATSA), which it has used against Turkey, Iran, North Korea and Russia.

Despite Washington’s warnings, New Delhi moved forward with the purchase, arguing that it has strategic connections with both Russia and the U.S.

Turkey has also gone forward with its S-400 purchase, dismissing the U.S. sanctions threat and saying the missiles are a matter of national security.

U.S. President Joe Biden’s Coordinator for Sanctions Policy James O’Brien told lawmakers in the House of Representatives last week that the U.S. does not want India to buy the S-400 missile defense system from Russia, according to media reports.

He also said that Washington has to take into account important geostrategic circumstances in response to the growing demand from Biden to exempt India from CAATSA.