Israel has reached a $1 billion preliminary deal to buy 30 Italian military training jets, Israeli defense officials said Thursday, providing a long-awaited upgrade to what is widely viewed as the most advanced air force in the Middle East.

The agreement, which still needs formal government approval, marked the end of a long competition between Italy and South Korea over the lucrative sale.

Israel announced it would buy the M-346, made by the Italian company Alenia Aermacchi and designed for low-cost flights. The aircraft will replace American Skyhawks, which the Israeli Air Force has trained with for 40 years. As early as 2008, the Israeli air force announced it needed to replace the antiquated jets.

Italy will reciprocate the Israeli purchase by buying $1 billion in Israeli defense equipment, Israel’s Defense Ministry said.

The ministry’s director general, Udi Shani, said the offset deal enabled Israel to make the large purchase in a “harsh budgetary reality.’’

South Korea hoped to sell its T-50 aircraft to Israel and had issued a $1.6 billion counteroffer including buying the expensive Iron Dome anti-rocket system, defense officials said. As Israel considered its options, South Korea complained about a lack of transparency in the deal.

The officials spoke on condition of anonymity because they were discussing internal deliberations.

In a letter to South Korea, Shani wrote that “after close analysis of both the proposals, and at the conclusion of a long and comprehensive review process, it was decided that the Italian proposal was the most efficient choice for Israel’s Ministry of Defense.’’

He cited the suitability of the jets to the “direct needs’’ of the Israeli air force, the cost and the “significant offset conditions.’’

The deal only has initial approval and needs official authorization from Israel’s defense minister, the government, and the Israeli parliament. Defense officials said they expect the agreement to get the final green light, and the planes to be delivered in 2014.

Alenia Aermacchi noted that the aircraft has just been delivered to the Italian air force and, shortly, will also be in service with Singapore’s military.

“We would like to thank the Israeli Ministry of Defense for their trust in and their choice of the M-346, a fact that confirms the product’s excellence,’’ Alenia Aermacchi’s CEO Giuseppe Giordo said in a statement.

Israeli possesses a sophisticated air force of U.S.-made F-15 and F-16 warplanes, and its pilots spend considerable time on training flights. Even reservists, for instance, must spend one day a week in the air. Officials said the new planes would be critical for Israel to maintain its edge.

The need for a strong air force is especially critical at a time when Israel has been hinting at potential military action against Iran’s nuclear program.

Military analyst Yiftach Shapir of the Institute for National Security Studies said the new planes would give an important boost, noting the aging Skyhawks are “long past their life service.’’

“Training will be better, pilots will be better prepared for the combat aircraft they will be flying, and everything will be cheaper because the aging aircraft really needed a lot of maintenance,’’ he said. (AP)