NEW DELHI >> Seizing on their personal bond, President Barack Obama and Indian Prime Minister Narendra Modi said Sunday they had made progress on nuclear cooperation and climate change, with Obama declaring a “breakthrough understanding” in efforts to free U.S. investment in nuclear energy development in India.

Obama and Modi expressed hope that a landmark 2008 nuclear agreement between the U.S. and India could begin to bear fruit.

“We are committed to moving towards full implementation and this is an important step that shows how we can work together to elevate our relationship,” Obama said.

The two countries had been at an impasse over U.S. insistence on tracking fissile material it supplies to India and over Indian liability provisions that have discouraged U.S. firms from capitalizing on a 2008 civil nuclear agreement between the U.S. and India.

“In our judgment, the Indians have moved sufficiently on these issues to give us assurances that the issues are resolved,” said Ben Rhodes, Obama’s deputy national security adviser.

Rhodes said it would still be up to U.S. companies to assess the market and decide whether they wanted to partake. He said neither country needed to take legislative action to complete the agreements the leaders reached Sunday.

In a joint appearance following their meetings, both men went out of their way to illustrate how their personal chemistry was yielding progress on various fronts, from defense, to trade to energy issues.

“Barack and I have formed a bond, a friendship,” Modi said. “We can laugh and joke and talk easily on the phone. The chemistry that has brought Barack and me closer has also brought Washington and Delhi closer.”

Obama said: “Your election and your strong personal commitment to the US-India relationship gives us an opportunity to further energize these efforts.”

Under hazy skies Sunday, Modi greeted Obama with a hug on the airport tarmac and offered an elaborate welcome at the country’s sprawling presidential palace. Obama also solemnly laid a wreath at a memorial honoring the father of India’s independence movement, Mahatma Gandhi.

On Monday, Obama was to be the guest of honor at India’s Republic Day festivities, making him the first U.S. president to attend the anniversary of the enactment of country’s democratic constitution.

Taking some of the luster off the trip, Obama is cutting his trip short to go to Saudi Arabia Tuesday to pay respects to the royal family following the death of King Abdullah. In doing so, the White House had to cancel a tour by the president and first lady of the Taj Mahal, the famed white marble monument to love in the city of Agra.

Other international topics also dogged Obama on his trp.

Obama said the administration is “deeply concerned” about the latest deadly flare-up in eastern Ukraine, where authorities said indiscriminate rocket fire killed at least 30 people in Mariupol, in the southeast, on Saturday. But Obama insisted that he won’t change the way he’s been handling the situation. He said he’ll keep trying to isolate Russia and would review options short of military conflict with Russia over Ukraine.

On Yemen, which has been a close U.S. ally in the fight against terrorism, Obama denied that the political vacuum created there last week has affected U.S. counterterrorism operations inside the Middle Eastern country. Obama said recent news reports to the contrary are inaccurate.

“We continue to go after high-value targets inside of Yemen and continue to maintain the pressure that’s required to keep the American people safe,” he said.

The normally bustling streets of New Delhi were empty and the sidewalks cleared by Indian police as Obama’s motorcade sped from the palace to Gandhi’s memorial. A massive security presence was in place for Obama’s visit, with numerous roadblocks and armed men lining the streets.

Obama and Modi strolled briefly through the picturesque gardens of Hyderabad House, the guest house where the leaders held their talks, walking past little ponds of lotus flowers. Sitting down before cups of tea, both men looked relaxed and smiled and laughed often as they chatted animatedly.

Earlier, Obama walked in his socks into a walled courtyard to lay a large white wreath at the site where Gandhi, India’s independence icon, was cremated. He then shoveled dirt and poured a pitcher of water around a young tree planted in his honor at the memorial.

As Obama and Modi opened their talks Sunday, the prime minister presented the president with a copy of 1950 telegram from the United States congratulating India on the adoption of its constitution.

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Associated Press writer Muneeza Naqvi in New Dehli and Darlene Superville in Washington contributed to this report.