The administration has notified Congress of its intention to sell 900 satellite-guided Joint Direct Attack Munitions to Saudi Arabia for 120 million dollars, State Department spokesman Sean McCormack said late Monday.
The weapons are the first part of a planned 20-billion-dollar deal with the Gulf which the administration announced last July.
The notification kicks off a 30-day period during which Congress can raise objections.
A US official did not deny that the notification had been deliberately timed to coincide with Bush’s visit.
The arms deal, which includes weaponry and high-tech munitions, has alarmed Israel and some US Congressmen, especially as Saudi Arabia refuses to recognise the Jewish state.
The administration, which has also announced a 30-billion-dollar military aid pact with Israel, argues the deal with the Saudis is needed to counter Iran.
The US president has made clear that what he calls the threat to the world posed by the "the world’s leading state sponsor of terror" is top of the agenda of his Middle East tour.
"The United States is strengthening our longstanding security commitments with our friends in the Gulf — and rallying friends around the world to confront this danger before it is too late," he said in a keynote speech in the neighbouring United Arab Emirates.
But diplomats said Bush faced "difficult talks" in Saudi Arabia which is determined to further conflict in the region after the US-led invasion of Iraq of 2003.
In the face of the war of words between Tehran and Washington, Riyadh has called for restraint, with Foreign Minister Prince Saud al-Faisal saying: "We are keen that harmony and peace should prevail among states of the region."
Bush arrived in Riyadh on Monday to a critical reception from the Saudi press for the outspoken attack on the Iranian regime he delivered in Abu Dhabi the previous day.
Bush’s speech in Abu Dhabi was "a display of the fairly muddled thinking behind the current foreign policy of the United States", said the Saudi Gazette, which like other Saudi newspapers generally reflects official thinking.
The Al-Watan newspaper said Bush needed to listen more to the Gulf Arab neighbours of Iran.
No details emerged after the US president’s first round of talks with Abdullah over dinner at the Riyadh palace which also serves as his residence.
Tuesday’s talks take place at the king’s ranch in Janadriyah, 40 kilometres (25 miles) northeast of the capital.
A source in the Saudi ruling family who requested anonymity told AFP that king wanted to host Bush there because the US leader received him twice — in 2002 and 2005 — at his Prairie Chapel ranch in Crawford, Texas, when he was crown prince and de facto ruler.
A senior US official said Bush will court Riyadh’s diplomatic influence and financial muscle which "could make an enormous difference in places like the Palestinian territories, Lebanon, Iraq, Afghanistan and other locations."
The continuing high oil price was also likely to be on the agenda of Bush’s talks with the king, having already featured in his talks with other Gulf oil producers.
"There has been discussions of oil and energy along with other issues that have come up in these talks," Bush counsellor Ed Gillespie told reporters.
"They talked about the nature of the market and the vast demand that’s on the world market today for oil."
Bush and Abdullah are also expected to discuss efforts to combat terrorism, with the US administration believing its ally — the homeland of Al-Qaeda chief Osama bin Laden — still has "more to do".
