RIYADH, Saudi Arabia - Saudi Arabia confirmed on Friday that it has signed a deal to buy 84 new US fighter jets to maximize its defense capabilities as tension between the United States and Iran escalates following Teheran's threat to close the strategic Strait of Hormuz.

The $29.4 billion deal, which was signed on Dec 24 in Riyadh, will supply 84 new Boeing F-15SA aircraft, modernize 70 existing planes, and also includes munitions, spare parts, training and maintenance contracts, US officials said.

The deal, the single priciest US arms sale to a foreign country, was first unveiled in October 2010 as part of a $60 billion US arms sale to Saudi Arabia.

It "ensures the kingdom receives the highest possible defense capabilities to protect its people and land", Saudi Arabia's state news agency SPA quoted a defense ministry spokesman as saying.

The announcement came amid rising tensions between Iran and the United States after Teheran threatened to close the Strait of Hormuz to oil tankers if Washington implements new sanctions over its nuclear program.

Victoria Nuland, a spokeswoman for the US State Department, said on Thursday that Iran had exhibited "irrational behavior" by threatening to close the strait.

The US Navy also confirmed on Thursday that the US aircraft carrier USS John C Stennis and the guided-missile cruiser USS Mobile Bay crossed through the Strait of Hormuz without incident.

A senior Iranian military commander dismissed the US warnings over Teheran's threats to close the strait.

Deputy Commander of Iran's Islamic Revolution Guards Corps (IRGC) Brigadier General Hossein Salami said on Thursday that Teheran does not seek Washington's permission to implement defense strategies in the Persian Gulf, the local satellite Press TV reported.

Administration officials described the advanced F-15s as designed to bolster overall Saudi defenses in an uncertain region.

But the sale was "not solely directed" toward Iran, said Andrew Shapiro, assistant US secretary of state for political-military affairs. "This is directed toward meeting our partner Saudi Arabia's defense needs," he said.

Tensions between Iran and Saudi Arabia were stoked earlier this year after the US accused Iran of plotting to assassinate the Saudi ambassador to the US in Washington earlier this year.

Yin Gang, an expert on Middle East studies at the Chinese Academy of Social Sciences, said the arms sale is not necessarily related to Iran's ongoing military exercises in the Strait of Hormuz.

"The US will still sell the arms to Saudi Arabia regardless of Iran's military exercises," said Yin.

"But the arms sale will greatly boost the military strength of Arab nations to overwhelm that of Iran and enhance their ability to rival Iran," Yin said.

Ye Hailin, a researcher with the Institute of Asia-Pacific Studies of the Chinese Academy of Social Sciences, said Saudi Arabia is also eager to acquire the weapons in order to achieve its ambitions in the region. "Saudi Arabia's military buildup is important for the US, so US arms sales to Saudi Arabia are a normal affair," he said.

On Thursday, China's Foreign Ministry confirmed on its website that Deputy Foreign Minister Zhai Jun visited Iran on Wednesday and Thursday to conduct regular political consultations between the foreign ministries of the two countries. Both sides exchanged views on China-Iran relations and international and regional issues of mutual concern, it said.

China Daily - Agencies