Indian and Russian officials rejected American pressure to downgrade their close defense ties on Monday as the two countries’ leaders met in New Delhi and agreed to extend military technical cooperation for another decade.

At a summit between Indian Prime Minister Narendra Modi and Russian President Vladimir Putin, both sides said they were proceeding with delivery of S-400 surface-to-air missile systems from Russia to India despite the threat of U.S. sanctions on India.

Agreements...

Indian and Russian officials rejected American pressure to downgrade their close defense ties on Monday as the two countries’ leaders met in New Delhi and agreed to extend military technical cooperation for another decade.

At a summit between Indian Prime Minister Narendra Modi and Russian President Vladimir Putin, both sides said they were proceeding with delivery of S-400 surface-to-air missile systems from Russia to India despite the threat of U.S. sanctions on India.

Agreements signed also included a contract for a joint venture in India to manufacture more than 600,000 Russian-designed AK-203 assault rifles, which will replace the INSAS model used by the Indian military for three decades.

India is acquiring Russian S-400 surface-to-air missile systems, in an example of the Russia-India cooperation on military matters.

Photo: Kirill Kukhmar/Zuma Press

But India’s Foreign Secretary Harsh Vardhan Shringla said the two sides couldn’t conclude a deal on using logistics at each others’ ports and military bases that would mirror pacts India has with the U.S. and several American allies.

“It’s being put off for some time,” Mr. Shringla told a news conference, without elaborating.

He described the S-400 purchase as a legacy contract while echoing other Indian officials in asserting an independent foreign policy.

The summit has thrown into sharp relief the obstacles facing the U.S. as it tries to persuade India to distance itself from Russia—long its main arms supplier—and boost defense ties with Washington to help counter China’s growing assertiveness.

While the U.S. is ultimately expected to waive sanctions over India’s S-400 purchase, it has urged India not to go ahead with the deal, warning that it could jeopardize future military cooperation with the U.S.

India says it reserves the right to choose its own arms suppliers and needs the S-400 to boost defenses on the border with China, which last year saw one of the bloodiest clashes since a brief border war in 1962.

Indian Defense Minister Rajnath Singh called for more military technical collaboration with Russia, including advanced research and co-production of defense equipment, to help India meet its “legitimate, real and immediate” defense needs.

“The pandemic, the extraordinary militarization and expansion of armament in our neighborhood and unprovoked aggression on our northern border since early summer of 2020 have thrown in several challenges,” Mr. Singh said.

Russia’s defense ministry said the agreement on military technical cooperation for the next decade implied cooperation between the branches of the armed forces of both countries, as well as the supply and development of weapons and military equipment.

India and Russia flags flew Monday outside Hyderabad House in New Delhi, as the two countries deepened defense ties.

Photo: T. Narayan/Bloomberg News

Russia’s Foreign Minister

Sergei Lavrov said the S-400 deal was progressing as planned, despite the U.S. pressure in India.

“We witness attempts on the part of the United States to undermine this cooperation and to make India obey the American orders, to follow the American vision of how this region should be developed,” Mr. Lavrov told reporters following talks with his Indian counterpart, Subrahmanyam Jaishankar.

“And our Indian friends clearly and firmly explained that they are a sovereign country and it will decide on whose weapons to buy and who is going to be a partner in this and other areas.”

India could face U.S. financial sanctions over the S-400 deal under the 2017 Countering America’s Adversaries Through Sanctions Act, or CAATSA, which names Russia as an adversary alongside North Korea and Iran. Last year, the U.S. sanctioned Turkey under CAATSA for buying the S-400. However, several influential U.S. senators have urged President Biden to waive the sanctions on India.

Mr. Lavrov said Moscow expressed its concern over U.S. activities in the region, such as the recent AUKUS security pact under which Britain and the U.S. will help Australia to build nuclear submarine capabilities.

He added that India had “clearly distanced itself” from the AUKUS bloc, while participating in the Quadrilateral Security Dialogue that includes the U.S., Australia, India and Japan.

Indian officials didn’t echo those comments publicly but stressed that Delhi had a privileged relationship with both Moscow and Washington.

Mr. Modi said in his opening remarks at the summit that friendship between India and Russia had remained constant and strong over the years despite fundamental changes taking place globally, and new geopolitical alignments emerging.

Mr. Putin highlighted Russian cooperation with India in a number of areas, including energy, high technology and space, mentioning the training of Indian cosmonauts as one subject that was discussed.

But he said Russia cooperated with India in the military-technical sphere “like with no other country,” citing development of high-tech military products and production, including in India.

Under the contract signed during the summit, a joint venture called Indo-Russian Rifles Pvt Ltd will produce 601,247 Kalashnikov AK-203 assault rifles over the next 10 years at a factory in the northern Indian state of Uttar Pradesh, according to Indian officials.

The plant would begin production within the next few months and local production of assault rifles should reach 100% in the future, Kalashnikov said.

“Russian and Indian specialists have done a lot of preparatory work over three years to optimize the price and technological parameters of the project,” Kalashnikov cited Vladimir Lepin, the company’s CEO, as saying. He added that the joint venture “undoubtedly opens a new page in Russian-Indian military-technical cooperation.”

Write to Rajesh Roy at rajesh.roy@wsj.com, Jeremy Page at jeremy.page@wsj.com and Ann M. Simmons at ann.simmons@wsj.com