RFERL - Turkish President Recep Tayyip Erdogan is expected to ask U.S. President Donald Trump to drop an Iran sanctions case against a wealthy Turkish-Iranian businessman on a visit to Washington on May 16.

Erdogan, who meets with Trump at the White House in the afternoon, has been lobbying for the release of Reza Zarrab, who is charged with acting as a go-between to help Iran's revolutionary guards and other Tehran clients evade U.S. sanctions.

Court documents made public last month revealed that Zarrab's attorneys, led by former New York Mayor Rudolph Giuliani, met with Erdogan on the case in February and afterwards attempted to initiate Zarrab's release from jail through a diplomatic process. Erdogan has since openly called for Zarrab's release.

Giuliani's law firm is registered as a foreign agent for Turkey and Giuliani also has close ties with U.S. President Donald Trump, having advised Trump during his campaign last year. A former prosecutor, Giuliani appeared on a list of potential Trump nominees for FBI director this week.

Guiliani's ties with both Trump and Turkey have been under intense scrutiny by the Manhattan judge in the Iran sanctions case, who asked at one point whether Giuliani was working for Erdogan or Zarrab. On May 15, the judge demanded to know more about Giuliani's ties to Trump.

Giuliani has made no secret that he is trying to arrange a "political" settlement of the case between Washington and Ankara, using Zarrab's past associations with Erdogan as a bargaining chip.

In 2013, U.S. prosecutors say Erdogan pressured Turkish prosecutors to drop criminal charges in a high-level bribery case brought against Zarrab. Erdogan's pressure as then-prime minister resulted in the firing of the prosecutors who brought the charges against Zarrab.

U.S. prosecutors say the 2013 charges pertained to a massive bribery scheme executed by Zarrab involving the payment of tens of millions of dollars to Cabinet-level Turkish officials and high-level bank officers in Turkey to facilitate Zarrab's transactions on behalf of Iran.

Ahmet S. Yayla, a George Mason University professor and former Turkish prosecutor, wrote in Modern Diplomacy this week that Erdogan wants the U.S. case against Zarrab dropped because his government was involved in the scheme to help Iran circumvent sanctions.

Erdogan knows "Zarrab is going to testify against him unless Turkey finds a way to save him from prison," Yayla wrote.

In visiting Trump at the White House, Erdogan is also expected to press two other major demands on Trump: to extradite cleric Fethullah Gulen, who Erdogan blames for an attempted coup against him last year, and to stop arming Syrian Kurdish rebels who he believes are linked to Kurdish "terrorist" groups in Turkey.

Yayla said he believes Erdogan will use the U.S. lease on the vital Incirlik air base in southern Turkey as leverage to pressure Trump to accede to his demands.