US officials portrayed Iran as a growing spectre that was engaged in aggressive expansion and destabilising the region.
The Bush administration announced on Monday the huge arms sales package to Saudi Arabia and other Gulf state allies aimed at creating a bulwark against Iran. Speaking before a Gulf state conference at the Egyptian resort of Sharm el-Sheikh, Ms Rice said: "There isn't a doubt that Iran constitutes the single most important single-country strategic challenge to the United States and to the kind of Middle East that we want to see."She and the defence secretary, Robert Gates, who are an on a two-day trip to the region, discussed the details of the proposed arms sales and military aid with the Arab countries directly involved.
Iran, which expressed alarm over the sales, accused Washington of creating an arms race to help the US defence industry. Syria, an ally of Iran, echoed this, with its foreign ministry saying yesterday: "He who wants to make peace does not start out with an arms initiative."
Nick Burns, the US undersecretary of state who is to follow Ms Rice and Mr Gates to the region, shrugged aside the Iranian and Syrian criticism: "These countries stand for everything we stand against."
The US wants Iran to cease work on a uranium enrichment programme that Washington claims is aimed at building a nuclear weapons capability. Iran denies the charge. Washington also accuses Iran of arming insurgents in Iraq, the Taliban in Afghanistan, and Hizbullah in Lebanon.
The arms package involves $20bn for the Saudis and the Gulf states, $13bn for Egypt and $30bn for Israel. It includes warships for the Saudi fleet in the Gulf. As well as Saudi Arabia, Egypt and Jordan, the conference yesterday was attended by Bahrain, Kuwait, Oman, Qatar and the United Arab Emirates.
A senior US defence official involved in the talks told reporters the sales were intended to send a message to the region: "We have been here 60 years and we're going to be here a lot longer."
Both the Saudis and the Gulf states, which are predominantly Sunni, fear Iran could try to stir up their Shia population.
The arms sale is part of a US strategy aimed at putting a squeeze on Iran that involves everything short of war. Both Ms Rice and Mr Gates are advocates of this approach, in contrast to the US vice-president, Dick Cheney, who argues that in the end military strikes will be needed.
Ms Rice, Mr Gates and Mr Burns hope the pressure can force Tehran to the negotiating table. The Whte House has been disappointed with two rounds of US-Iranian talks in Baghdad on Iraq.
The Arabs welcomed the proposed sales to help contain Iran. But they were cool towards pleas to give diplomatic and economic support to the Iraqi government.
"All parties need to really now throw their weight behind this effort for national reconciliation," Ms Rice said.
Ms Rice and Mr Gates flew to meet King Abdullah of Saudi Arabia. The US defence official argued it was in the interests of the Saudis and other Arabs to back the Iraqi government so it can be "an obstacle to Iranian influence ... not a bridge".
The Saudis and other Arab states view with suspicion the Iraqi prime minister, Nour al-Maliki, a Shia. The Saudis have described him as an Iranian agent.
The arms sales need to be approved by Congress, where there is concern about providing more arms to the region, particularly Saudi Arabia, and what would happen if the country collapsed.
Ms Rice is also seeking support for an international conference on the Israeli-Palestinian conflict but several Arab states have voiced little enthusiasm.
