U.S. President Joe Biden on Wednesday congratulated Indian Prime Minister Narendra Modi for his election victory, and Washington said it looked forward to further cooperation with New Delhi to ensure a free Indo-Pacific region.

"The friendship between our nations is only growing as we unlock a shared future of unlimited potential," Biden said in a posting on social media platform X.

Modi, whose National Democratic Alliance retained power with a surprisingly slim majority in voting results announced on Tuesday, said he had received a call from Biden.

"[I] Conveyed that India-U.S. comprehensive global partnership is poised to witness many new landmarks in the years to come. Our partnership will continue to be a force for global good for the benefit of humanity," Modi said on X.

The United States and India have deepened ties in recent years given shared concerns about China's growing power, even though New Delhi has maintained its long-standing relationship with Russia despite the war in Ukraine, and human rights issues.

In a statement issued shortly after Biden's congratulatory message, the U.S. State Department said Washington looked forward "to continuing to further our partnership with the Indian government to promote prosperity and innovation, address the climate crisis, and ensure a free and open Indo-Pacific region."

State Department spokesperson Matthew Miller on Tuesday called the U.S.-Indian relationship "a great partnership," although the U.S. had concerns about human rights, which it would continue to raise openly with New Delhi.

Ties have been tested by the discovery of assassination plots against Sikh nationalists in Canada and the United States. In November, U.S. authorities said an Indian government official had directed the plot in the attempted murder of Gurpatwant Singh Pannun, a Sikh separatist and dual citizen of the United States and Canada.

Last month, the U.S. ambassador to India said Washington was satisfied so far with India's moves to ensure accountability in the alleged plots, but many steps were still needed and there must be consequences for what was a "red line for America."

Political analysts say Washington has been restrained in public criticism of Modi because it hopes India will act as a counterweight to an expansionist China.