By Ori Lewis
JERUSALEM (Reuters) - Israel must not let the Gaza Strip's Islamist Hamas rulers dictate terms of a ceasefire after a recent escalation of fighting, Foreign Minister Avigdor Lieberman said on Monday.
Calm returned to Gaza Strip and southern Israel overnight after four days of cross-border violence in which 19 Palestinians died, with United Nations and Egyptian mediators having helped to negotiate a truce.
Lieberman, who leads the ultranationalist Yisrael Beiteinu party, a main coalition partner in Prime Minister Benjamin Netanyahu's government, told Israel Radio that Hamas would use any lull to regroup before another round of fighting.
"The aim of calm is a serious mistake because calm is used (by Hamas) to smuggle more and more arms," Lieberman said, adding that Hamas was obtaining increasingly powerful rockets.
"At this rate they will also reach Tel Aviv," he said.
The latest violence began last Thursday when Hamas militants hit an Israeli school bus with an anti-tank rocket, critically wounding a teenager. This attack sparked the worst fighting since a 2008-09 Israeli offensive into Gaza.
However, neither side appeared keen on a major confrontation, indicating they wanted to avoid escalation.
"Our central aim must be to stop the arms smuggling by Hamas but a second aim must be to topple the Hamas regime. As long as Hamas ... continues to act in terror attack mode ... this is unacceptable," Lieberman said.
The foreign minister, who espouses a hard line on security in Netanyahu's government, is not usually the one to determine Israel's defense and foreign policy moves, largely the province of Netanyahu and Defense Minister Ehud Barak.
Lieberman said that any failure by Netanyahu and his rightist Likud party to implement a tougher approach to Gaza militants would not cause a crisis in the government.
"We are not planning to leave the coalition, we will gain all that we agreed and signed with the Likud without threats and without a coalition crisis," he said.
Political analysts say Lieberman is looking to outflank Netanyahu, whose own Likud electorate has moved steadily to the right. Some suspect he covets the top job and may feel it is within reach if Likud is perceived as being "soft" on Hamas.
The timing of the latest Gaza conflagration was seen by some analysts as an effort by Hamas to divert attention from demands, fueled by pro-democracy unrest in the Arab world, for an end to its split with Fatah, the Western-backed Palestinian movement dominant in the West Bank.
(Editing by Crispian Balmer and Mark Heinrich)