Israel’s apparent decision to hold off on a full-scale invasion of the Gaza Strip and instead conduct more limited ground incursions, at least initially, aligns with suggestions that the U.S. defense secretary, Lloyd J. Austin III, made to his Israeli counterparts in recent days, American officials said on Saturday.
Biden administration officials warned that it was hard to tell what Israel would eventually do, since increased airstrikes and expanded ground incursions in the past three days indicated a more aggressive posture.
Prime Minister Benjamin Netanyahu of Israel said on Saturday evening that Israeli forces had entered the Gaza Strip on Friday to begin “the second stage of the war,” though he did not describe the move as an invasion. Military officials said earlier on Saturday that Israeli troops had pushed into the northern part of the enclave and remained there on Saturday evening.
So far, the incursions into Gaza by Israeli ground forces are smaller and more narrowly focused than what Israeli military officials initially described to Mr. Austin and other top U.S. military officials, American officials said on Saturday.
Indeed, the initial Israeli invasion plans alarmed U.S. officials, who expressed concern that they lacked achievable military objectives and that the Israeli military was not yet ready to launch a ground invasion.
In phone conversations with his Israeli counterpart, Yoav Gallant, Mr. Austin has stressed the need for careful consideration of how Israeli forces might conduct a ground invasion of Gaza, where Hamas maintains an intricate network of tunnels under densely populated areas.
The Israelis improved and refined their plan after a concerted effort by Mr. Austin and other officials, a U.S. official said on Saturday, speaking on condition of anonymity to describe war planning between allies. However, Biden administration officials have insisted that the United States had not told Israel what to do and still supports a ground invasion.
Other factors that also most likely influenced Israel’s war planning, American officials say, are the possible impact on hostage negotiations and the fact that Israeli political and military leaders have been divided about how, when and even whether to invade.
But current and former Pentagon officials, as well as former U.S. commanders who have conducted urban military operations, said on Saturday that Israel appeared to be conducting a phased operation, with smaller reconnaissance units advancing into Gaza to locate Hamas fighters, clash with them and identify their vulnerabilities.
“Once the weaknesses, seams and gaps are discovered, they bring in the main assault force,” said Mick Mulroy, a former top Middle East policy official at the Pentagon and a retired C.I.A. officer.
Frederick B. Hodges, a retired three-star Army general who served in Iraq, said the tactic also seemed to be a way for Israeli forces “to reduce or limit casualties as well as collateral damage” to buildings.