(CNN) A suicide bombing in Kabul on Wednesday that claimed the lives of more than 90 people and injured at least 11 US contractors was the latest jolt to Washington that the US is still fighting its longest war in Afghanistan 16 years after it began.

The massive bombing was carried out in a secure area of Kabul at the height of the Wednesday morning rush hour, exploding in the diplomatic quarter near the German Embassy and the Afghan presidential palace.

The attack occurred as President Donald Trump is currently weighing a recommendation sitting on his desk to add another 3,000 to 5,000 US troops in Afghanistan to accelerate the training of Afghan forces.

The troop levels for Afghanistan will be Trump's first major decision on the 16-year war. By and large, Afghanistan was little more than an afterthought during the presidential campaign, taking a backseat to Trump's focus on defeating ISIS and terrorism. And so far as president, Trump has said little about the Afghan war beyond requesting a strategy assessment from the Pentagon.

The troop decision has split the White House, with National Security Adviser H.R. McMaster and Defense Secretary James Mattis advocating for additional troops, while Steve Bannon and others from his camp pushing back over the president straying from his "America First" campaign pledge.

"I expect the debate inside the White House runs much deeper than any single suicide attack in Afghanistan," said Luke Coffey, a foreign policy analyst at the Heritage Foundation and an Army veteran who served in Afghanistan. "This wasn't the first such attack today in Kabul, and it certainly won't be the last."

JUST WATCHED US citizens wounded in deadly Kabul blast Replay More Videos ... MUST WATCH US citizens wounded in deadly Kabul blast 01:11

While US troops were not injured in the blast, the bombing served as a deadly reminder of the deteriorating security situation in Afghanistan.

Gen. John Nicholson, the top US commander in Afghanistan, told the Senate armed services committee in February the fight with the Taliban was a "stalemate." There are 8,400 US troops and 6,000 NATO troops in Afghanistan, and Nicholson said there was a shortfall of a few thousand needed to tip the balance.

ISIS has also proven to be a rising threat in Afghanistan — the group claimed responsibility for Wednesday's attack, although the Afghan intelligence service accused the Haqqani Network in Pakistan of carrying out the bombing — and the most headline-grabbing action in Afghanistan during Trump's presidency was the first use of the so-called "mother of all bombs," which hit ISIS targets.

Afghan Ambassador to the UK Said Tayeb Jawad told CNN's Clarissa Ward Wednesday that Afghanistan needs sustained international military assistance.

"The bulk of the fight is done by the Afghans," he said. "But there are some capabilities that are missing. ... We would like to have more international troops -- US, NATO, and other countries -- to stay with our troops for a little bit longer, to train and assist us effectively, so we can deal with this threat."

It's too soon to say whether the bombing, one of the deadliest in Kabul in recent years , would have any impact on the president's troop decision. A senior administration official told CNN Tuesday that an announcement on Afghanistan would not come this week.

"At a strategic level, this kind of terrible tragedy reminds us that the mission is not going great — but it also underscores the kind of people we are up against, and the importance of winning (or at least not losing)," Brookings defense analyst Michael O'Hanlon said in an email.

Divisions in Congress, too

The reaction on Capitol Hill Wednesday was one mostly of condemnation of the attack, with few statements touching on the underlying divisions over the US role in Afghanistan going forward.

"The Afghanistan attack is a tragic reminder that the war on terror is not over," tweeted Republican Sen. Johnny Isakson of Georgia. "We must remain steadfast w/allies so that peace can prevail."

The Afghanistan attack is a tragic reminder that the war on terror is not over. We must remain steadfast w/allies so that peace can prevail. — Johnny Isakson (@SenatorIsakson) May 31, 2017

Rep. Eliot Engel of New York, the top Democrat on the House Foreign Affairs Committee, said the attack underscored the Trump administration's lack of a strategy to end the Afghan conflict.

"Donald Trump might like the feeling of dropping the Mother of All Bombs, but it won't bring stability and it isn't a plan to prevent future attacks," Engel said in a statement. "Rather, we need to train Afghan security forces and promote a political solution to bring an end to the violence."

Afghanistan has often been a source of partisan division, with Republicans repeatedly slamming President Barack Obama for his efforts to withdraw all US forces there, a position he retreated from to end up at 8,400 US troops when Trump took office.

At the same time, a small group of Republicans and Democrats have long been pressing for the US to stop sending troops to Afghanistan altogether, arguing that the 16 years of war shows no end is in sight, with or without a US presence there.

Richard Fontaine, president of the Center for a New American Security, said Wednesday's attack was likely to harden the resolve on both sides of the debate.

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"I think it could easily lead to a hardening of positions rather than pulling people toward a consensus about a way forward, which puts all the emphasis on the president," Fontaine said. "What does he want to do? Are we going to get more involved or less involved?"

The NATO question

Trump was expected by some in Washington to announce his Afghanistan troop decision while he visited NATO on his recent foreign trip.

Instead, Trump's speech did not reaffirm the US commitment to the alliance's collective defense, and he scolded NATO countries for failing to meet the shared target of spending 2% of GDP on defense.

Trump's rhetoric could be in the back of the mind of NATO countries if the US comes seeking a larger troop commitment in Afghanistan.

"I'm not sure Europe is more willing to contribute troops post-trip than they were before the trip," Fontaine said.

Tony Cordesman, a defense analyst at the Center for Strategic and International Studies, said the Trump administration is considering adding a relatively small number of troops when put in context to previous increases, but he bemoaned the "ambiguous and contradictory" message coming from the White House over its plans for the Afghan War.

And he predicted Trump would have to stay out of his own way in order to successfully lead the NATO coalition to a more stable Afghanistan.

"The real problem may not be a bomb in Kabul," Cordesman said. "It may be a tweet in Washington."