India's main federal opposition Congress party on Tuesday said that the deployment of Russian-made S-400 "Triumf" anti-aircraft missile systems by China at the Ladakh border poses a “grave threat" to Indian security interests in the region.

"This is the first time that they [People’s Liberation Army] have deployed the S-400 at the border. It is a grave threat to us and the government must take all steps to ensure that the issue [border standoff] is resolved", Congress spokesperson Pawan Khera said at a press briefing.

According to reports, the PLA’s Western Theatre Command has stationed S-400 systems at the Nyingchi airbase, which is around 20 kilometres from the disputed Line of Actual Control (LAC) border in the eastern Ladakh region.

“The government has to be reminded time and again about the threat lurking at the border. In fact, all the Indians must be made aware of the threat at the border”, said Khera.

“How far are the Indian aircraft in Jammu and Kashmir and Ladakh from these S-400s?” asked the Congress leader.

The opposition spokesperson said that the blame for the Chinese actions at the border rested squarely with the prime minister, as he slammed Narendra Modi for giving a “clean chit” to Beijing over the border dispute.

PM Modi said at an all-party meeting on 19 June last year that ”nobody has entered” Indian territory, just three days after deadly clashes between the Indian Army and the PLA left 20 Indian troops and four Chinese soldiers dead. The episode marked the deadliest border incident between the two Asian powerhouses in over four decades.

“That day [19 June] will be remembered as a black day in the history of the country. That statement from the prime minister has emboldened China”, said the Congress spokesperson.

Khera claimed that Modi was “more worried about his artificial strongman image” than maintaining the territorial integrity of the country. “We have a strong army with a weak prime minister who is afraid even to name China”, he said.

Khera pointed out that Modi's policy towards China directly contributed to the increase in transgressions, as he drew attention to the PLA's reported incursions in Uttarakhand and Arunachal Pradesh states last week.

He further questioned why bilateral trade between India and China was witnessing an increase, despite the ongoing border dispute.

“The two-way trade between an enemy country like China and India rose by 62 percent (as per official figures released by Beijing) in the first eight months of this year, compared to the same period last year. Trade can wait”, stated Khera.

The Congress leader also blasted the Indian PM for not being able to convince China to vacate the territories patrolled by India until May 2020, when the border standoff erupted.

“The PLA had entered the Depsang Plains in 2013, when Manmohan Singh [then-Congress leader] was the Prime Minister. But they left within 21 days of entering our territory”, recalled Khera.

He cited the 2005 and previous border management agreements between the two countries, going on to ask Prime Minister Modi as to why he was unable to make China adhere to these terms of the pact.

Military vehicles and equipment, parts of the S-400 air defence systems, are unloaded from a Russian transport aircraft, at Murted military airport in Ankara, Turkey, Friday, July 12, 2019 - Sputnik International, 1920, 05.10.2021

The most recent round of military commander-level talks between the two nations on 10 October, aimed at finding a solution to the standoff, ended in a stalemate. The PLA’s Western Command accused India of persisting with “unreasonable” demands during the negotiations.

"Instead of misjudging the situation, the Indian side should cherish the hard-won situation in China-India border areas", Colonel Long Shaohua, spokesperson for the Western Theatre Command of the People's Liberation Army (PLA), said.

India, meanwhile, reiterated that China’s “unilateral” attempts at altering the status quo at the LAC were responsible for the current crisis. An official statement by India after the meeting on 10 October said that China "could not provide any forward-looking proposals" in response to New Delhi's "constructive suggestions" to resolve the faceoff.

The PLA and the Indian Army have been embroiled in a standoff in the region for over a year, having held 13 rounds of military commander-level discussions as well as high-level meetings in a bid to resolve the standoff.

The troop disengagement process between the two sides commenced in February this year. So far, the Indian Army and PLA have disengaged troops in the Galwan Valley, the northern and southern banks of Pangong Tso Lake, and the Gogra Post.

Reports in the Indian media suggest that China has refused to back down on its claims in the Depsang Plains and Hot Springs, with the former strategically located at the tri-junction with Pakistan-administered Kashmir.