AHMEDABAD, India - U.S. Secretary of State John Kerry is in India to attend an international investment conference and push trade ties with the giant South Asian nation ahead of visit by President Barack Obama later this month.

Kerry arrived in the capital of Gujarat state, Ahmedabad, on Sunday to lead the U.S. delegation to the Vibrant Gujarat Investment Summit. The gathering seeks to promote responsible sustainable development.

India's prime minister will open the conference and Kerry will see him to discuss plans for Obama's upcoming trip to participate in India's annual Republic Day ceremonies.

In Ahmedabad, Kerry will also hold talks with the prime minister of the tiny Himalayan kingdom of Bhutan, a rare cabinet-level meeting between the two nations.

Kerry stopped briefly in Germany on Saturday to meet with the ailing ruler of Oman, the Mideast country that's served an important intermediary role in negotiations over Iran's nuclear program.

Kerry spent about 90 minutes with Sultan Qaboos bin Said, 74, who has been receiving medical treatment in Germany since November. Kerry later tweeted that he was "grateful for strong friendship" with the sultan.

Among the topics they covered were the Iran talks, which are set to resume this coming week in Switzerland; the situation in Yemen; the Syrian civil war; the terrorist attacks in Paris; and tensions between Israelis and Palestinians.

Oman hosted several secret meetings between U.S. and Iranian officials in the months leading up to an interim nuclear deal in November 2013.