"If Israel carries out its threat, it has to shoulder the responsibility for the deterioration of the security condition," Ismail Radwan, a Hamas spokesman, told Xinhua.
"Any attempt to reoccupy that area will fail," Radwan added.
His remarks followed reports that the Israeli army was preparing to send its troops to the borderline, known also as the Philadelphi Route, to prevent arms smuggling into Gaza.
The report, published by Israel's Jerusalem Post newspaper, said that Hamas, which took over Gaza by force in 2007, has built up its military arsenal by bringing in long-range missiles from Syria and Iran through the tunnels across the border.
Israel evacuated the area in 2005 when it withdrew all troops and settlers from the Gaza Strip. Forces loyal to President Mahmoud Abbas controlled the borderline from the Palestinian side until Hamas overran them in 2007.
Media reports said that Egypt has recently started to curb smuggling from its side by building an underground barrier to destroy the tunnels.
Cairo has not officially announced the building of a steel barrier under its borders with Gaza; however, some government officials said it is Egypt's right to defend its borders and protect its national security.
The barrier has caused a crisis between Hamas and Egypt. For Hamas, the tunnels are the only lifeline for Gaza in the light of an Israeli blockade on the territory.