Blatter recently retained Richard Cullen, the chairman of the law firm McGuireWoods and a former US federal prosecutor, said a person familiar with the matter, who spoke to Reuters on condition of anonymity.
Separately, Blatter's top lieutenant, Valcke, has hired prominent New York defence attorney Barry Berke, a second source said.
Blatter, 79, announced on June 2 that he would stand down as FIFA president, only four days after he was re-elected to the position, saying he had lost the mandate from the entire world of football.
That followed US authorities' indictment of nine current and former FIFA officials and five corporate executives for allegedly running a criminal enterprise that involved more than $150 million in bribes over 24 years.
US prosecutors have not accused Blatter or Valcke of wrongdoing. However, they believe Valcke was involved in $10 million in FIFA bank transactions that are a key part of the investigation, a source said in early June.
Valcke said last week that while he had signed off on the transactions he had done nothing wrong, adding that allegations against him are "insanity."
Among the issues the FBI is examining is Blatter's stewardship of FIFA, sources have said. Blatter became president in 1998 and remains in the job pending an election that likely will not occur before December.
Investigations by US and Swiss authorities include scrutiny of how FIFA awarded World Cup hosting rights to Russia and Qatar.
Blatter has also retained Lorenz Erni, a top lawyer in Zurich, the first source said. Erni declined to comment earlier this week.
TIES TO COMEY
It was unclear whether the decisions by Blatter and Valcke to hire top US lawyers indicated increased scrutiny of them by US authorities. It is common in the United States for even potential witnesses to seek legal advice if they can afford it in order to protect their rights.
Cullen was not immediately available for comment on Wednesday. A spokeswoman for US prosecutors declined to comment.
FIFA could not immediately be reached for comment outside business hours.
Prosecutors in Switzerland, where FIFA is based, have identified 53 suspicious bank transactions and could summon Blatter and Valcke for questioning, Michael Lauber, the Swiss attorney general, told journalists on Wednesday.
Cullen has long ties to FBI director James Comey, whose bureau is conducting much of the FIFA-related investigation. Comey served as a federal prosecutor in Richmond, Virginia, where Cullen is based, and worked as a partner at McGuireWoods. Cullen spoke positively of Comey's nomination for FBI director in 2013.
As a lawyer, Cullen has often represented government officials as they tried to fend off indictments in high-profile criminal investigations.
He represented Tom DeLay, a Texas Republican and former majority leader of the US House of Representatives, during the investigation into corrupt Washington lobbyist Jack Abramoff. DeLay was not charged.
Another client was Ken Melson, who was pushed out of his job as acting director of the US Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF), but did not face charges, after a botched anti-gun-smuggling operation known as "Fast and Furious."
Cullen also represented CIA and U.S. Defence Department officials in an investigation into interrogation techniques dating to the George W. Bush administration, according to his law firm biography.
In Richmond, about 110 miles (177 km) south of Washington, DC, Cullen resides largely outside the political and media spotlights of Washington and New York. McGuireWoods has its home office in the city, and Cullen has worked there with only brief interruptions since law school.
But he is a power broker in Virginia Republican politics. He has worked closely with governors and local lawmakers, according to a 2007 profile in Richmond Law magazine. In February, he helped bring Republican presidential hopeful Jeb Bush to Richmond for an event, the website Politico reported.
Cullen left his law firm in the early 1990s to serve as the chief federal prosecutor for the Eastern District of Virginia, which sits just outside Washington.
EXPERIENCE WITH BANKERS
Berke, a partner at Kramer Levin Naftalis & Frankel, most recently represented Michael Steinberg, a portfolio manager at Steven A. Cohen's SAC Capital Advisors hedge fund. Steinberg was sentenced last year to 3-1/2 years in prison after being convicted of engaging in insider trading.
Previously, Berke in 2011 secured the acquittal of Raymond Craig Brubaker, a former broker for Deutsche Bank charged in connection with a massive tax shelter scheme.
He also represented the investment bank Bear Stearns. In that case, he persuaded prosecutors - in the same US Attorney's Office in Brooklyn that is pursuing the FIFA investigation - not to charge the bank in connection with the collapse of two funds during the subprime mortgage crisis, according to his law firm biography.
Image: FIFA president Sepp Blatter (left) with secretary general Jerome Valcke.
Photograph: Ruben Sprich/Reuters
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