Hamas is interested at this stage in maintaining the lull in fighting against the Israel Defense Forces along the Gaza Strip border, defense officials suggested Monday.

Likewise, Egypt is keeping up heavy pressure on Hamas leaders in Gaza not to deviate from the understandings reached with it regarding the suspension of fighting.

Defense Minister Ehud Barak said Monday that if the rocket fire from the Strip and arms smuggling cease, "The door to another reality will open," but he added that "we are still far" from that reality.

Barak added that Israel will not negotiate with Hamas, "except for indirect talks regarding kidnapped soldier Gilad Shalit."

Under the agreement Cairo reached with Hamas three weeks ago, Hamas would stop launching rockets at Israel for a week-long trial period. Israel announced that quiet on the Palestinian side would result in corresponding quiet from Israel. So far, both sides are keeping their promise to Egypt, even though Islamic Jihad occasionally launches rockets into Israel.

On Sunday, Egypt released 33 Hamas operatives who were arrested in Sinai after the Rafah border fence was breached in late January. This is a significant gesture by Cairo, evidently intended to "bolster" the lull. IDF sources said Egypt seems to be making an especially intense effort to preserve the lull.

Four mortar shells fired from Gaza struck the western Negev causing no casualties or damage on Tuesday.

IDF sources confirmed that Hamas is also refraining at this time from supplying rockets to other Palestinian factions.

Security sources told Haaretz that the lull should not be viewed as an agreement between Israel and Hamas. They say Egypt was motivated to reach understandings with Hamas for interests of its own and out of fear the violence would spill over into its territory. Israel merely "hitched a ride on an arrangement already reached between Hamas and Cairo," the sources said.

However, senior military commanders indicated this week that the lull is expected to be temporary, because Egypt will have a hard time securing an overall agreement due to the massive distance between the sides.

The head of the Defense Ministry's Political Department, Amos Gilad, who is in charge of the talks with Cairo, has been instructed to take a tough negotiating line with Egypt. In an interview Monday on Army Radio, Gilad made an evident effort to deny any connection between the talks he is conducting and Egypt's talks with Hamas.

"There are no negotiations here whatsoever," Gilad said.

He described the purpose of his mission as "bringing about a cessation of rocket fire and a halt to the smuggling of material."

On Monday, there was an increase in the number of incidents along the Gaza Strip border. At least one rocket and several mortar shells were fired at the western Negev, and IDF troops were fired on near the perimeter fence. There were no casualties.