Egypt's foreign minister says no more Palestinians will be allowed to come over from Gaza, threatening to "break the legs" any new illegal infiltrators.
Egyptian forces have largely avoided border confrontations
"Anyone who breaches the border will have their legs broken," Ahmed Abul Gheit said in a television interview.
Many Egyptians were openly sympathetic to the plight of their Gaza neighbours when they streamed across the border last month to stock up on supplies.
Frontier defences were blasted away by militants defying an Israeli blockade.
Mr Abul Gheit met US Deputy Secretary of State David Welch to discuss the situation in Gaza on Thursday, four days after Egyptian forces sealed the last gaps in the border.
His earlier threatening remarks came during a late-night interview on state television, in which he criticised Israel and Gaza's de facto rulers, Hamas, for creating the instability.
He blamed Israel for imposing "collective punishment" on Gaza in response to rocket attacks, and he described Hamas's self-styled resistance as a "laughable caricature" which harmed the perpetrator more than the enemy.
A Hamas spokesman in called the remarks "inappropriate" and said he did not believe they reflected the official Egyptian stance.
"All we want is an open border crossing," said Sami Abu Zuhri said.
"Instead of making these threats against the Palestinian people, he should voice his anger against the Israeli occupation, which is what is closing the border crossings between Gaza and Egypt."
Egypt is Israel's longest-standing Arab ally, and has been holding talks with the Palestinian Authority, based in the West Bank, and Israel about future border arrangements.
Clashes broke out on Monday when crowds of Palestinian youths threw stones at an Egyptian border post. Guards responded with tear gas, before gunfire erupted from both sides of the border.