S enior Israeli officials are acknowledging that some enriched uranium may have survived the powerful U.S. strikes on Iran's key nuclear sites last month.

What many have called a "fragile" ceasefire between Israel and Iran remains in place following nearly two weeks of missile strikes, which included the U.S. dropping "bunker-busting" bombs on Iran's three nuclear sites. But questions remain about how much damage the operation actually did.

Iran's president signaled a more diplomatic tone amid heightened tensions and distrust over nuclear negotiations weeks after both Israel and the United States launched strikes aimed at ending Iran's nuclear program. His remarks suggest Iran is looking to ease international pressure and avoid escalation.

Pentagon reports Iran's nuclear facilities were "completely obliterated" in June strikes, offering a more optimistic assessment than earlier estimates while Iran acknowledges damage.

The Pentagon on Wednesday sharpened its assessment of Iran's nuclear program, declaring that Iran's ability to build a nuclear weapon following the U.S. strike on its nuclear facilities is "closer to two years" away.

The process of uranium enrichment increases the concentration of U-235, an isotope that can sustain a nuclear chain reaction. Beginning in 2006, the U.N. Security Council called on Iran to suspend all uranium enrichment, but it endorsed the JCPOA on July 20, 2015.

With questions mounting over the impact of the U.S. and Israeli onslaught on Iran’s nuclear facilities and military infrastructure, a return to hostilities could be a matter of when, not if.

President Donald Trump said on Friday that Iran had not agreed to inspections of its nuclear program or to give up enriching uranium.

Experts long argued that airstrikes alone would not be capable of permanently ending Iran's nuclear program absent negotiations.

After the strikes, Trump said “Iran’s key nuclear enrichment facilities have been completely and totally obliterated.”

The United Kingdom, France and Germany have agreed to restore tough U.N. sanctions on Iran by the end of August if there has been no concrete progress on a nuclear deal, two European diplomats said Tuesday.