(NEW YORK) -- The Israel Defense Forces need "a few more weeks" to fully degrade Iranian military capabilities, such as missile-launchers, a senior Israeli security official told ABC News.
The Israeli security official poured cold water on the idea that a substantive deal between the United States and Iran could be reached within President Donald Trump's earlier deadline of this weekend. Trump said Thursday that he was postponing plans to target Iran's power plants until April 6 citing ongoing talks.
The Iranians "are very well-trained negotiators," the security official said. "They won't agree in a few days to end all the actions."
The senior Israeli security official, who spoke to ABC News on the condition of anonymity as he was not authorized to speak to the media, said he was worried that U.S.-Iran talks could lead to a deal which does not extract significant enough concessions from the Iranians.
The Israeli security official said that if he were advising U.S. negotiators he would ask "to see actions [from the Iranians] that can be measured."
"For example, giving [up] all the 400 kilograms of enriched uranium," he added.
Iran has previously denied U.S. and Israeli accusations that it was enriching uranium to near weapons-grade level, with an ultimate aim of producing nuclear weapons.
The Israeli official spoke to ABC News on Tuesday, the day after Trump posted on his social media platform that there had been "very good and productive conversations" between the U.S. and Iran "regarding a complete and total resolution of our hostilities in the Middle East."
Iranian officials have denied -- at least publicly -- that negotiations with the U.S. are taking place. On Wednesday, Iran's Foreign Ministry spokesman, Esmaeil Baqaei, told Indian TV that there were "no talks or negotiations" between Iran and the United States.
"No one can trust U.S. diplomacy," Baqaei added.
However, on Thursday a Reuters report quoted an Iranian official as saying that a U.S. proposal for ending the war was “one-sided and unfair."
The White House said in a statement that the U.S. military had been "decimating Iran's military capabilities with overwhelming firepower, skill, lethality, and force."
"The United States is winning very decisively and way ahead of schedule," a White House official said.
"We have taken major strides towards completing our military objectives, to the point that we are close to completing them," the White House added.
On Thursday, Trump announced a further pause in plans to hit Iran's power plants, again citing talks that he said were "going very well."
An Israeli military official who was authorized to speak with journalists told reporters during a briefing Wednesday that the Israeli Air Force had conducted 8,500 strikes in Iran since the end of February and had destroyed some 400 Iranian ballistic missiles and 335 missile-launchers, which equated, he said, to about 70% of Iran's overall arsenal of missile-launchers.
However, when the military official was pressed by reporters on the extent to which the IDF's military operations and goals were outstanding in the war, he declined to give details, stressing that the U.S. and Israeli militaries were "well-coordinated" and working "shoulder-to-shoulder."
"We are achieving more and more of our objectives," said the military official , who is part of the IDF division that coordinates operations deep inside enemy territory.
"War is not a one bang and it's over. It's an ongoing machine," he added.
The senior Israeli security official who spoke anonymously to ABC News said the speaker of Iran's Parliament, Mohammad-Bagher Ghalibaf, was leading the talks with the Trump administration.
Ghalibaf's apparent leading role in negotiations, which has not been confirmed by the U.S. or Iran, was first reported by Axios.
On Monday, Trump refused to confirm which senior Iranian official the U.S. was in talks with, telling reporters, "I don't want him to be killed" and referring to the Iranian lead negotiator as "a top person."
The senior Israeli security official described Ghalibaf, who is a former commander of the Islamic Revolutionary Guard's Air Force, as "an extremist" and "not Mother Teresa" and told ABC News that Israel would refrain from attempting to kill Ghalibaf while the talks continue.
"He has this kind of insurance [policy] as long as he talks," the official said, adding, "no one is secure in Iran."
Asked by a reporter if the IDF was holding off on any attempts to kill Ghalibaf, the military official did not comment directly about Ghalibaf but stressed that, in terms of its list of targets, the IDF would accept and follow any political decisions.
Earlier this week, the Trump administration sent a 15-point plan to Iran end the war, via Pakistan, which has emerged as a key mediator, two sources familiar with the plan told ABC News Tuesday.
Those sources said the plan addresses Iran's ballistic missile and nuclear programs as well as maritime routes but would not provide any other details including which Iranian officials the proposal was sent to. It is also unclear whether Israel has signed onto the proposal.
While diplomatic efforts continue, the Pentagon is preparing to deploy as many as 5,000 additional troops to the Middle East, with some of those forces already in transit.
The troops are a mix of U.S. Army paratroopers and Marines.
However, exactly when the troops will arrive or where they will land is not clear.
Trump has indicated that the negotiations between U.S. and Iranian officials have, in part, been focused on Iran's control over the Strait of Hormuz.
Iran's stranglehold over that narrow waterway, through which around a fifth of the world's oil and gas normally passes, has caused a spike in energy prices and volatility in trading on financial markets.
The senior Israeli security official who spoke anonymously with ABC News said Israel was working on the assumption that Iran had laid naval mines in the Strait of Hormuz.
The Israeli official stressed that locating naval mines and disarming them is a "complicated" task.
"If one big oil tanker were exploded by a few naval mines, it would play havoc with markets, as well as the insurance for shipping companies, and would send the price of oil skyrocketing," the Israeli official said.
"If Iran says they have mined the Strait of Hormuz then the basic assumption we must have as commanders ... is that they have mined the Strait of Hormuz," said the Israeli military official who briefed reporters.
In possible talks Israel wants the U.S. to press Iran to give up what remains of its enriched uranium and rein in its proxies in the region, the senior Israeli security official stressed.
That Israeli official suggested that it would not be possible to seize Iran's enriched uranium by military force.
The two U.S. Marine Expeditionary Units which are being deployed to the Middle East, "don't have the engineering tools" to conduct an operation to "pull out" Iran's remaining enriched uranium from underground sites, he said.
Asked about this issue on the briefing with reporters, the military official declined to comment.
The Pentagon declined to comment about the senior Israeli official's assessment of remaining objectives in the war and the U.S. military's capabilities.
The White House said the war on Iran was "a conditions-based operation" and said it would conclude when the president "determines that our objectives are met."