Senior Israel Defense Forces officials said Monday that Hamas officials had ordered the armed wing of the Islamist group to target Israeli soldiers who still remain inside the Gaza Strip, despite cease-fire declarations from both sides.

Israeli officials have said that a complete withdrawal from the Gaza Strip would likely be completed before the inauguration of the U.S. President Barack Obama on Tuesday.

So far, no attempt to harm an Israeli soldier has been reported.

Earlier Monday, Hamas vowed to rearm in defiance of any Israeli and international efforts to prevent the group from replenishing its arsenal of rockets and other weapons following the Gaza war.

"Do whatever you want," said Abu Ubeida, a spokesman for Hamas' armed wing, "manufacturing the holy weapons is our mission and we know how to acquire weapons."

Addressing journalists with his face masked by a checkered Arab scarf, Ubeida said "all options would be open" if Israel failed to pull its troops out of the Gaza Strip within a week, a demand raised by Hamas when it announced on Sunday a cease-fire after three weeks of fighting.

Israel, which declared its own ceasefire hours before, has threatened to renew military action if Hamas tries to smuggle more weapons into the Gaza Strip.

Israel wants Egypt to prevent arms from reaching Palestinian militants through tunnels running under the border with the Gaza Strip.

On Friday, Israel signed a security accord with the United States that calls for increased information-sharing, technical assistance and the use of various U.S. "assets" to prevent weapons from getting to Hamas from air, land or sea.

Meanwhile, six key European leaders on Sunday pledged to work to prevent Hamas from rearming. The commitments were offered both at the Sharm al-Sheikh summit in Egypt and at a meeting in Jerusalem with Prime Minister Ehud Olmert.

They offered to provide troops and technological assistance to prevent Hamas from smuggling weapons and terrorists into the Gaza Strip, in cooperation with Egypt and the United States.