When India and Pakistan stood on the brink of war in 1999, President Bill Clinton waded into the crisis with personal diplomacy, forceful letters and stern warnings, threatening tough economic action against Islamabad unless it backed down.

But as tensions escalated last week between India and Pakistan, President Donald Trump and many of his senior aides were preoccupied with a high-stakes summit with North Korea, as well as a heated congressional hearing featuring his former personal lawyer, Michael Cohen.

It was the most serious confrontation between the South Asian nuclear-armed rivals in decades, but the Trump administration was effectively a bystander -- it did not seek to mediate the standoff as the U.S. has in the past, several former and foreign diplomats told NBC News.

Activists of Pakistani Peoples Party (PPP) burn an effigy of Indian Prime Minister Narendra Modi during an anti-Indian protest in Karachi on March 1, 2019. Asif Hassan / AFP - Getty Images file

"The U.S. government doesn't appear to be engaged on this issue at a senior level," said Daniel Feldman, former special representative to Afghanistan and Pakistan under the Obama administration. "It demonstrates not only a lack of focus, but how diminished our capacity is with so many senior positions, across a number of key agencies, vacant or held by acting officials."

At the height of the crisis last week, Secretary of State Mike Pompeo, national security adviser John Bolton and Joint Chiefs Chairman Gen. Joseph Dunford made phone calls to their counterparts in Islamabad and New Delhi, which were important but not close to the type of shuttle diplomacy that played out in previous crises, former officials said.

In 1999, Clinton worked the phone with both of his counterparts and helped resolve the showdown. But that was not the case this time.

"For the first time in over 20 years, Washington was not an active player in trying to calm down an Indo-Pakistani crisis," said Bruce Riedel, a former CIA officer who served on the National Security Council under Clinton. "The president didn't talk to the protagonists."

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Administration officials rejected the criticism, saying the United States was one of the first governments to condemn the suicide bombing last month that killed 40 Indian troops -- triggering the crisis -- and repeatedly appealed to both sides to defuse the conflict. Pompeo "played an essential role in the de-escalation of tensions between India and Pakistan," speaking to leaders in both countries and his counterparts, a State Department spokesperson said.

Washington was also in continuous contact through the U.S. embassies in New Delhi and Islamabad, the spokesperson said, adding: "While not all diplomacy can be conducted in public view, the United States will continue to engage with India and Pakistan to de-escalate tensions through all appropriate channels."

Washington has no ambassador to Pakistan and it was only in December that the White House finally submitted a nomination for the senior position at the State Department that oversees South and Central Asia. Other senior State Department positions handling South Asia have undergone frequent turnover, and former officials say the White House has often had other priorities that have pushed aside the long-running dispute between India and Pakistan over Kashmir.

Former Defense Secretary James Mattis, well-versed in the history and politics of South Asia, stepped down in December after clashing with the president over Syria and international alliances. His successor, Patrick Shanahan, is a former Boeing executive inexperienced in foreign policy.

"In the past, we've been the sheriff in this region. Now, there's no one in our police station who's willing to intervene," said Henry Sokolski, a former Pentagon official and now executive director of the Nonproliferation Policy Education Center. "Who is our diplomat who is going to intervene here?"

At least one U.S. agency had concerns in the past few months that tensions were rising between the two adversaries. The concerns prompted the CIA to beef up its commitment to the region, two U.S. officials, who were not authorized to speak on the record, told NBC News. They offered no further details.

Other regional experts said while Washington had played a more limited role, India and Pakistan were not necessarily keen to see the Trump administration serve as an interlocutor. Unlike previous standoffs, the Trump White House was ready to grant India the room it needed to resolve the situation.

"It has been a little less of an aggressive posture by the United States to try to intervene, but that's mostly by design because India is a much different place than it was 15, 20 years ago," said Rick Rossow, senior adviser at the Center of Strategic and International Studies think tank.

Washington sees India as "a responsible player," with sufficient power and skill to take care of its interests, he said.

As the U.S. has grown frustrated with what it considers Pakistan's failure to crack down on extremists, Washington's ties with Islamabad have frayed while it has forged increasingly close ties to India, a country it sees as a crucial counterweight to China, according to Shuja Nawaz of the Atlantic Council think tank.

"This has been the policy for some time now. There's been a discernible shift to India starting with the Bush administration, and it stayed on course during the Obama period and has continued under Trump," Nawaz said.

Although the crisis appeared to ease after Pakistan released a captured Indian fighter pilot last Friday, the two sides exchanged artillery fire over the weekend in the disputed province of Kashmir, killing several civilians. And the underlying disagreements — over Kashmir and Pakistan's support for militants — remain unresolved.

The standoff was triggered by the Feb. 14 suicide bombing that killed 40 Indian troops in Indian-controlled Kashmir. The militant group Jaish-e-Mohammed claimed responsibility for the attack, and India responded with an airstrike inside Pakistani territory that it said targeted a training camp for the militants. Pakistan retaliated by sending aircraft to bomb targets in India. In a dogfight, both sides claimed to have shot down aircraft, and an Indian fighter pilot was captured after his plane went down. Islamabad then released the pilot Friday in what it called a conciliatory gesture.

By ordering the first air raid across Pakistan's border since 1971, Indian Prime Minister Narendra Modi signaled his government would respond sharply to terrorist attacks it believes are linked back to Pakistan, and he has cited Israel as a model for his approach.

The stakes are now higher for the next time tensions erupt, and former officials said the Trump administration appears ill-prepared, with its chaotic decision-making and chronic understaffing.

"This is a wake up call," Riedel said. "The Trump team is not ready for a real world crisis. It's been lucky for two years."