Indian Prime Minister Narendra Modi and Russian President Vladimir Putin met on the sidelines of a regional summit in China on Monday in a show of deepening ties when New Delhi’s relations with Washington are strained over the purchase of Russian oil.

The two leaders held talks after attending the key session of the Shanghai Cooperation Organization gathering in the port city of Tianjin, where discussions focused on regional stability and bilateral cooperation.

In his remarks opening the talks, Putin addressed Modi as a "dear friend" and hailed Moscow's ties with New Delhi.

"Russia and India have maintained special relations for decades. Friendly, trusting. This is the foundation for the development of our relations in the future," Putin said.

Modi used the meeting to welcome the peace initiatives aimed at halting the conflict between Russia and Ukraine and called on the stakeholders to move forward constructively.

At the talks, Putin was accompanied by a large delegation that included top government officials.

Russian state media reported that before sitting down for the formal dialouge, Putin and Modi spoke one-on-one for almost an hour in Aurus, a high-end, Russian-made limousine that Putin regularly brings on foreign trips.

The meeting carried added significance as it came days after U.S. President Donald Trump imposed an additional 25% tariffs on Indian imports, raising the total duties to a steep 50%, in retaliation to India’s continued purchases of discounted Russian oil.

Washington has repeatedly warned New Delhi against buying Russian crude which it said was partly keeping Moscow’s revenues afloat to fund the fighting in Ukraine.

India has defended its imports as essential for meeting its growing energy needs of 1.4 billion people.

Modi travelled to Russia twice last year. The first was a visit to Moscow for talks with Putin in July. He then traveled to Kazan in October for the summit of the BRICS bloc of developing economies.

Russia has had strong ties with India since the Cold War, and New Delhi’s importance as a key trading partner has grown since the conflict between Moscow and Ukraine.