Earlier this year when President Obama visited Hiroshima, the site where the U.S. dropped a nuclear bomb 71 years ago on Saturday, the president said leaders must have the courage to pursue a world without nuclear weapons.

One expert, however, says the president is unlikely to take any substantial steps towards that end during his last six months in office.

"It's not clear how bold the administration is planning to be. My sense is not very bold," said Jeffrey Lewis, director of the East Asia Nonproliferation Program at the James Martin Center for Nonproliferation Studies.

Current policy allows for nuclear weapons to be used in retaliation for a nuclear attack on the U.S. or its allies, but also in response to a large-scale ground invasion or a biological or chemical attack. The administration is considering changing that to say that the U.S. could only use nuclear weapons in retaliation for a nuclear attack.

Lewis, however, said this declaration wouldn't be binding on Obama himself or any president down the line.

"Does any of this truly matter? I don't think so," he said. "Even if Obama said he wouldn't use it first, that doesn't bind [Hillary] Clinton in six months. Frankly, if she said it, it wouldn't bind her six months down the line."

Donald Trump, the GOP nominee, has reportedly asked officials briefing him why the United States can't use the nuclear weapons it has.

Kingston Reif, director for disarmament and threat reduction policy at the Arms Control Association, said that the U.S. already has a "de facto" no first-use policy. Still, he said it would be a significant and "far-reaching" policy change to formally declare it. While when to use nuclear weapons is a presidential decision, meaning the next president could do whatever he or she wanted regardless of any changes Obama makes before leaving office, Reif said there would be "significant" pressure not to change it back.

The second reform, which Lewis said has been given the green light, would reaffirm a United Nations security council commitment to prohibit nuclear explosive testing around the world, both analysts said.

This, however, is also not legally binding, Lewis said.

The administration has promised that more changes to work towards a non-nuclear world will be coming before the end of Obama's term in January.

"I can promise you today that President Obama is continuing to review a number of ways he can advance the Prague agenda over the course of the next seven months," Ben Rhodes said in June at an Arms Control Association event, referencing Obama's first major nuclear speech after taking office. "Put simply, our work is not finished on these issues."

Other things under consideration, according to Reif, include the size of the stockpile needed to keep the country safe and extending the 2010 New Start agreement, a nuclear arms reduction treaty with Russia that is set to expire in 2021.

Reif said that the administration has also begun a review of whether the nuclear modernization plan it came up with at the start of Obama's tenure is still the right one, given the constrained budget environment, especially if nuclear modernization is taking money out of maintenance accounts for more conventional weapons. But it wouldn't be completed before Obama leaves office and would simply serve to inform the next president's modernization plan.

Todd Harrison, director of defense budget analysis at the Center for Strategic and International Studies, said this week that the Obama administration could delay or cancel some major upcoming modernization and procurement programs, like long-range stand off missile or the ground-based strategic deterrent. But doing so would only mean taking it out of the fiscal 2018 budget request, a product which Obama will ultimately have no final say over.

"The Obama administration is just going to hand that budget request over to the new administration. The new administration could put those things back in before they submit it to Congress. So we'll have to wait and see," Harrison said.