The White House on Thursday threw its full support behind Israel's military response to a barrage of rockets fired by the Islamist Palestinian movement Hamas that rules the Gaza Strip. Deputy National Security Adviser for Strategic Communications Ben Rhodes said it would be "up to the Israeli government" whether to follow up punishing airstrikes with a ground assault.

"Our view is that the Israelis have the right of self-defense when their citizens are faced with the threat of indiscriminate rocket fire from within Gaza," Rhodes told reporters on a conference call.

Asked whether the Obama administration would have any issues with an Israeli ground assault, Rhodes replied that "ultimately, it's up to the Israeli government to make determinations about how they're going to carry out their military objectives."

The Associated Press has reported that Hamas fired more than 200 rockets on Thursday, killing three people, and that Israel seemed to be gearing up for a ground invasion of Gaza. The escalating conflict amounted to President Barack Obama's first major foreign policy test since winning re-election Nov. 6. Rhodes said American officials were in close consultation with their Israeli counterparts "to have an understanding of their plans going forward." The Obama administration has been in discussions with Turkey, Egypt and "some of our European partners," he said, thought to have sway over Hamas in order to get them to urge the militant organization to halt its rocket attacks.

"At the United Nations, where this is being discussed, we've sought to keep the focus where it should be—which is on Hamas's rocket fire as the precipitating cause here," Rhodes explained.

"What we've also said is that the best course of action would be for there to be a general de-escalation of the violence, but that the onus is on Hamas—and those with influence over Hamas—to help bring about that de-escalation, so that we don't see a widening conflict," he told reporters. "So we certainly want to see a de-escalation, we certainly want to see a broader conflict avoided."

The official noted that the White House has urged Israel to take "all steps ... to avoid civilian casualties." He added, "And we deeply regret the loss of life on the Israeli and Palestinian side."

Israeli Ambassador to the United States Michael Oren briefed key senators on the operation. The lawmakers—Democrats and Republicans—released a joint statement expressing "solidarity" with Israel while warning that "escalation will only lead to further suffering on both sides."