Democratic Party Senator from Connecticut Richard Blumenthal is chairing a permanent subcommittee on the investigation. 

He has written to the PGA Tour and LIV Golf, which is financed by Saudi Arabia's Public Investment Fund, asking for all documents relating to the shock collaboration.

"PIF's role as an arm of the Saudi government and PGA Tour's sudden and drastic reversal of position concerning LIV Golf raises serious questions," wrote Blumenthal.

"Prior to this agreement, PGA Tour was one of the loudest critics of LIV Golf's affiliation with Saudi Arabia."

Blumenthal's request also includes access to records relating to the Tour's non-profit status within a two-week deadline.

It is seen as a warning that its tax-exempt standing could be challenged, while corporate structure and records of disputes between leading figures is also demanded.

LIV Golf and the PGA Tour are yet to respond to Blumenthal's letter following their June 6 merger.

The US Congress does not have the power to block the agreement simply by opening the investigation, but it is thought that the scrutiny and public hearings could be politically damaging for the pair.

However, the Justice Department could also look into how the deal came about and attempt to halt it.

It is already scrutinising the anti-trust lawsuit regarding the PGA Tour's initial efforts to prevent players from joining LIV Golf.

US Secretary of the Treasury Janet Yellen has said that it is not clear whether the merger was a matter of national security but Senator Ron Wyden said US officials should determine whether it would give the Saudis "improper control or access to US real estate".

The merger follows huge disruption to the sport following LIV Golf's launch in June of last year and as those who participated in the new tour were banned from PGA events.

A new entity is yet to have a name and is set to benefit from "capital investment" from the PIF.