Billionaire and Israel Hayom newspaper owner Sheldon Adelson met with Israel Police investigators in order to make a statement regarding the Netanyahu-Mozes affair on Thursday.
Netanyahu is suspected in two separate criminal cases of abuse of office.
Adelson and his wife, Miriam, who is also expected to testify soon, arrived in Israel on Monday, at the same time as US President Donald Trump, to celebrate Jerusalem Day.
The File 2,000 investigation deals with suspicions that Netanyahu promoted in his meetings with Moses legislation that would harm Israel Hayom in exchange for positive coverage for the prime minister in Yedioth Ahronoth, on the eve of the March 2015 elections. The handout is staunchly pro-Netanyahu and it is Yedioth Ahronoth's main competitor.More news: 'Profound, Political Courage:' Christian Leaders React to Trump's Middle East Trip
More news: ABC releases SEC football game times for Week 1 of 2017 season
More news: Aziz: No order by ICJ on Jadhav's consular access
Adelson visits Israel regularly and was questioned near Tel Aviv on a trip, with authorities stating he is not a suspect in the investigation.
According to leaks of the conversation reported by Channel 2 in January, Netanyahu allegedly told Mozes he would ask Adelson, whom he referred to as "the gingy", or redhead, whether a Knesset bill to weaken Israel Hayom would be acceptable to him.
The couple attended the final speeches Netanyahu and Trump gave at the Israel Museum in Jerusalem on Tuesday just before the USA leader left the country. Its editors say it is independent and free of any political influence.
The second case Netanyahu is being investigated for involves businessmen giving gifts to the Prime Minister, breaching his role as a public servant.