US Defense Secretary Jim Mattis has said the US wants to resolve the standoff with North Korea diplomatically and is focused on denuclearising Pyongyang's nuclear weapons programme.

"We maintain the capability to deter North Korea's most dangerous threats, but we also will back up our diplomats in a manner to keep this as long as possible in the diplomatic realm," Mr Mattis told reporters in New Delhi, following talks with his Indian counterpart.

"Our goal is to solve this diplomatically," he said.

Mr Mattis' comments come amid escalating rhetoric between President Donald Trump and North Korean leader Kim Jong-un.

The Trump administration clarified Monday that it is not seeking to overthrow North Korea's government after Mr Trump tweeted over the weekend that Mr Kim "won't be around much longer." Pyongyang interpreted the tweet as a declaration of war.

Mr Mattis arrived in the Indian capital late Monday, marking the first visit to the country by a Cabinet-level official from Mr Trump's administration.

In meetings with Indian Prime Minister Narendra Modi and other officials, Mr Mattis was expected to focus on deepening defence cooperation between the two countries and discuss how India could contribute to US efforts in Afghanistan.

The talks with Indian Defense Minister Nirmala Sitharaman covered ways to enhance and complement efforts to restore security in Afghanistan as Washington steps up its own military campaign against Taliban insurgents who have gained ground.

Last month, while outlining his new strategy for Afghanistan, Mr Trump urged India to assist security efforts in Afghanistan.

Ms Sitharaman said India would continue its efforts to reconstruct Afghanistan's infrastructure, but she ruled out sending Indian troops to the country.

So far, New Delhi has contributed around $3bn (£2.2bn) toward building highways, power transmission lines and dams, as well as to aid public health and education in the war-ravaged country.

New Delhi will also enhance its efforts to train Afghan soldiers in counterterrorism and help build its police forces, Ms Sitharaman said.

India and the US also discussed maritime security in the Indo-Pacific, amid shared concerns about an increasingly aggressive China. The US, India and Japan annually conduct naval exercises in the Bay of Bengal to improve coordination between their navies.