Washington ? In April 1986, Vice President George H.W. Bush traveled to Saudi Arabia with a stern warning. Record low oil prices of $10 a barrel threatened the U.S. oil industry and U.S. national security. If prices don’t rise, he warned, perhaps a U.S. tariff on imported oil would do the job.

More than 22 years later, his son George W. Bush is on a similar mission, but with the opposite goal in mind. President Bush meets today with Saudi King Abdullah and will lobby for help in bringing down world oil prices, which have raced past $125 a barrel.

Then and now, the Saudis are the only oil power with enough unused production capacity to make a difference on price if they increase supply. But the hard fact is that the world oil market has changed, and Saudi Arabia is far from the only producer holding the fate of U.S. consumers in its hands. Even if the Saudis increase production, shortfalls elsewhere, along with rising global demand, can offset their efforts – and are.

Many Americans grumbling at the gas pump are quick to blame the Saudis for their woes – just as many might be surprised to learn that Saudi Arabia trails Canada and Mexico as the chief suppliers of foreign oil to the United States and isn’t far ahead of Venezuela, Nigeria and Angola. In 2006, Saudi Arabia provided only 14 percent of U.S. oil imports. Still, if it boosted production significantly, added world supplies would tend to drive global oil prices down, regardless of who bought their exports.

Saudi Arabia is the world’s only significant swing producer: Its oil production can be ratcheted up or down to lower or raise prices worldwide. (Iraq potentially could do the same if ever it achieved stability, but that’s not a near-term prospect.)

So what have the Saudis done since 2005, when oil prices climbed above $70 a barrel, then $80, then $90, and this year broke the once-unthinkable threshold of $100? They have increased production capacity, meaning that in a pinch they could make up the difference between global demand and available supply. They now can produce 11 million barrels per day, or bpd, and expect that number to reach 12.5 million bpd by 2010.

That’s why some Democrats in Congress, including New York Sen. Charles Schumer, are threatening to hold up a $1 billion-plus arms deal for the Saudis, a crucial ally in the global war on terror, unless the kingdom puts more oil on international markets.

“We are saying to the Saudis that, if you don’t help us, why should we be helping you?” Schumer said this week.

The Saudis are said to be reluctant to pump much more oil since U.S. oil inventories of late have been higher than five-year averages. That suggests that oil isn’t in short supply here, and that other factors, such as the weakening U.S. dollar and speculation in commodities markets, are driving up prices.

“I think the president has no intention whatsoever of having the Saudis put more oil in the market,” said Fadel Gheit, an industry analyst for Oppenheimer & Co. in New York. “If the president wanted the Saudis to do that, he would not have asked them publicly.”