WASHINGTON -- India has watched with wariness as President Obama's administration has lavished attention on rivals Pakistan and China. Now, Obama is trying to ease Indian worries by honoring Prime Minister Manmohan Singh on Tuesday with the first state visit of his presidency.

India will receive the elaborate welcome because the relationship quietly has become one of the most important the United States has. It is seen as crucial to the U.S.-led fight against extremists in Pakistan and Afghanistan, as a counterweight to China and as key to efforts to settle world trade and climate change deals.

Singh's visit, however, comes at a delicate time. Indians are bristling over a perception that Obama neglected India during his recent trip to Asia and seemed to endorse a stronger role for China in India's sensitive dealings with Pakistan.

The tension has disturbed a wave of goodwill between the countries orchestrated by former President George W. Bush, who oversaw the transformation of the relationship after decades of Cold War-era distrust. The new ties are symbolized by a landmark civilian nuclear cooperation accord signed into law last year after years of close communication among senior Indian and U.S. officials who negotiated and then sold the accord to lawmakers.

Obama and Singh are now consumed with steering their countries through tough economic times and with winning domestic political battles. That means less time spent nurturing a relationship that blossomed under Bush.

Indian elite classes are nervous about Obama, according to Teresita Schaffer, a former State Department South Asia specialist and U.S. ambassador to Sri Lanka.

"There's a certain amount of Bush nostalgia," she said. While Bush was seen as having an emotional connection to the country, she said, Obama's connection is seen as cerebral and as being eroded by domestic problems and by the focus on Afghanistan and Pakistan.

Because of the uncertainty, the leaders will be keen to show each other during Singh's visit that the partnership is still in good shape.

"Both sides will bend backward to demonstrate that they're committed to going forward on the relationship," said Ashley J. Tellis, a former adviser to a top negotiator on the nuclear deal.

The U.S. is especially interested in India's ability to help turn the tide against violent extremism in South Asia. U.S. officials are pushing Pakistan to focus its military attention on extremists along the border with Afghanistan, not on India, its neighbor and bitter rival.

Stronger U.S.-Pakistan ties, some in India feel, also could influence events in Kashmir, the Himalayan region divided between nuclear-armed Pakistan and nuclear-armed India.

Singh's visit follows Obama's meeting with Chinese President Hu Jintao in Beijing, a visit many in India watched closely.

Indian-Chinese trade is strong, but the countries have long bickered over a disputed border and fought a border war in 1962. Both sides regularly cross the long, unmarked boundary in orchestrated efforts to show sovereignty.

Some Indians are nervous about the U.S. reliance on China to tackle global crises.

There also has been heartburn in India over a joint statement by Obama and Hu that mentioned sensitive India-Pakistan ties. Some saw this as a hint that Obama wants Beijing more involved in South Asian diplomacy. The Indian Foreign Ministry shot down the idea of a "third country" role in India-Pakistan affairs.

C. Raja Mohan, a leading Indian strategic analyst, said at a Washington think tank that encouraging a stronger role for China in South Asia is like "welcoming the fox into the chicken coop."

"We don't want to be subordinate to the Chinese in South Asia," Mohan said.

On the eve of Singh's visit, a string of U.S. and Indian officials played down worries about China's role in South Asia.

Undersecretary of State William Burns warned against "too much reading into statements."

Bestowing upon Singh the first state visit of Obama's presidency, Burns said, shows the importance the U.S. administration gives to strong ties with India.

Indian officials speak of a seamless transition from the Bush to Obama administration, but they acknowledge that a certain reaffirmation of the relationship is always necessary when a new administration takes power.

The countries are cooperating on defense, energy, education, agriculture, economy and counterterror initiatives.

Sharp differences, however, exist on carbon emissions and whether India should be part of an international agreement setting legally binding limits on its emissions.