Israel won't carry out a large-scale military operation in Gaza at this time, Israel's prime minister said Saturday, despite the military's warnings of a Hamas arms buildup.

Israel fears that the Islamic militant Hamas is trying to copy the tactics of the Lebanese guerrilla group Hezbollah which fought Israel to a draw in last summer's war in Lebanon.

An Israeli military official said Saturday that Hamas has exploited a period of relative calm to smuggle large numbers of anti-tank missiles and 30 tons of weapons-grade explosives into Gaza, using tunnels under the border with Egypt. Hamas has also increased its militia, the so-called Executive Force, from 5,600 to 10,000 fighters, the official said, speaking on condition of anonymity in line with military regulations.

Hamas has dismissed such claims as Israeli propaganda. Earlier this month, the group formed a coalition with the Fatah movement of moderate Palestinian President Mahmoud Abbas. The new government said it's ready to consolidate a four-month-old truce, but has stopped short of renouncing violence.

In an interview broadcast Saturday, Israeli Prime Minister Ehud Olmert was asked whether a large-scale Israeli invasion of Gaza is needed to halt an arms buildup in Gaza.

"The question is if it has to be a military operation, if it has to be a military operation by us and if it has to be now," Olmert told Channel 2 TV. "We won't shy away from a military operation if we reach the conclusion, after a thorough check, that it is possible, based on logic and level-headedness and no exaggerations, that there is no better way than this."

Asked whether this was the case now, he said: "This is not the case."

Diplomatic constraints might keep Olmert from ordering a Gaza invasion at this time. The U.S. is trying to revive Mideast peacemaking by winning greater involvement of moderate Arab states, and a large-scale Israeli military operation could sabotage such efforts.

Also, Olmert is still fighting off criticism that he embarked on the war against Hezbollah hastily, without consultations. He might also be concerned about getting entangled in fighting in crowded Gaza; previous operations have caused many casualties, including among Palestinian civilians, drawing international condemnation but yielding few achievements for Israel.

Still, senior military commanders have repeatedly expressed concern about the arms buildup.

Last month, Israel's southern commander, Maj. Gen. Yoav Galant, warned that Iran is helping Hamas upgrade its fighting strength by providing technology, funding, and direct military training.

Galant said at the time that the training and technology has enabled Hamas to grow from a ragtag militia into a well-organized group resembling an army — complete with battalions, companies, platoons and special forces for surveillance, snipers, and explosive experts.

Also, the head of Israel's Shin Bet internal security agency, Yuval Diskin, said that dozens of Hamas operatives are going to Iran for training. He gave no proof for the allegation.