Britain and the United States are having a bit of bother over security arrangements for next summer's Olympic Games in London, sources tell The Guardian.

The London Organizing Committee of the Olympic and Paralympic Games, responsible for the events, now realizes it's initial estimate of 10,000 security personnel at 32 sports venues is inadequate, the Guardian newspaper said, quoting unidentified sources.

The actual number needed is apparently more than double that -- 21,000 -- and the private security firm hired for guards is now in a push to hire the shortfall, conduct background checks on those selected and train them amid a shortfall in funding to do so.

The United States, concerned that terrorists or others bent on mayhem could target U.S. athletes and diplomats at the games, is said to be planning to send 1,000 security personnel to Britain given security concerns, much to the dismay of British officials.

"We are not equal partners in this," a security official was quoted as saying. "They (the Americans) are being very demanding."

That is understandable. Olympic Games are prime targets for terrorists as history has shown, and London is no stranger to terrorist attacks.

In the 1972 Summer Olympics in Germany, Palestinian terrorists invaded the Israeli team village in Munich and killed 11 athletes and coaches, as well as one German policeman.

In Atlanta, two people died and 111 were injured in 1996 when a pipe bomb packed with nails exploded at the city's Centennial Olympic Park.

Security precautions at subsequent games have been high, so much so that Greece's original estimate of $122 million for security at the 2004 Olympics actually ended up at $1.8 billion, according to Businessweek

Security inside venues in Britain next year will not be the responsibility of British police but of G4S, the security company hired by the organizing committee.

Amid the controversy in Britain over the earlier, mistaken estimate of security personnel needed to deal with, and protect, the tens of thousands of venue visitors, the athletes and sports staff, Britain's Ministry of Defense -- struggling with budget cuts and force reductions -- has apparently offered about 3,000 troops for security duty during the games, with another 2,000 in reserve status.

Britain's new defense secretary, Philip Hammond, told Parliament "all necessary measures" would be taken to ensure security for the world gathering.

In answer to a question in the House of Commons from former Defense Secretary and Member of Parliament Liam Fox, Hammond said, "I can assure you that all necessary measures to ensure the security and safety of the London Olympic Games will be taken including, if the advice of the military is that it is required, including appropriate ground-to-air defense," according to a report in the Daily Mail.

That still doesn't answer the questions of where G4S will find qualified on-the-ground security personnel and who will pay for them.

U.S. government officials in Washington have not commented on the issue or reports of strong U.S. pressure for details of security plans and expressions of security concerns. But the U.S .Embassy in London said the United States was confident in Britain's security arrangement.

"The United States Embassy has the utmost confidence in the British Government's arrangements to ensure safety and security for the Olympic Games," Charge d'Affaires Barbara Stephenson said in a letter to The Guardian newspaper.

"The U.S. team is one of the largest participating in the Games, and thousands of American tourists are expected to attend Olympic events. It is, therefore, entirely normal and prudent for the U.S. to engage in discussions with U.K. officials about security arrangements for the Olympic Games."