Grassley asks in his letter how Veselnitskaya and her colleagues were allowed to say almost six months after the expiration of her visa.
The senator from the USA state of Iowa added that if necessary, he will subpoena Manafort.
"We're working very closely on this and we've already agreed that we're going to bring Manafort before our committee", Grassley said as quoted by the Des Moines Register.
Sen. Richard Blumenthal, a member of the committee, said it was "long overdue" that Manafort be called to testify.
Jacksonville native one of 16 killed in military crash in Mississippi
No more smoke is rising the day after the fiery crash of a US military plane in a field in rural MS , killing at least 16 people. At least one Hudson Valley resident was killed in the Stewart Air National Guard-based military plane crash in MS on Monday.
Also that month, a Washington lobbying firm that Manafort co-managed registered with the Justice Department as a foreign agent.
The Congressional investigation into Russia interference in the 2016 Presidential election was tensed on Wednesday after the legislators planned to question the former leader of the #trump campaign and decide whether the Russian social network trolls were involved in the short-term electoral efforts.
U.S. House of Representatives Speaker Paul Ryan on Thursday urged President Donald Trump's eldest son to testify to a congressional committee about alleged links between Trump's team and Russian Federation in the 2016 presidential election campaign.
"It is unclear how she was still in the country for that meeting, despite being denied a visa beforehand and her parole purportedly expiring on January 7, 2016", Grassley wrote, according to a statement and copy of the letter released Wednesday.
However, Veselnitskaya was able to come into the United States, after requesting a meeting with Donald Trump Jr. through an intermediary promising damaging information on political opponent Hillary Clinton.
Gymboree closing 350 stores after filing for bankruptcy; 7 in Pennsylvania
One of the stores set to close is the Gymboree store at SouthPointe Pavilions mall at 27th Street and Pine Lake Road. And two Janie and Jack stores will remain: Galleria and Taubman Prestige Outlets in Chesterfield.
"This raises serious questions about whether the Obama administration authorized her to remain in the country, and if so, why?"
"Obviously it would be appropriate for anybody to get into anything that went on at that meeting, and he was at that meeting", Grassley told Iowa reporters.
"In retrospect, I probably would have done things a little differently", Trump Jr. said.
Quentin Tarantino to make film based off Charles Manson Family murders
That's dark, even for Tarantino , whose characters tend to be criminals and vigilantes with morals-rarely cold-blooded murderers. In 1971, Manson and several of his followers were sentenced to life in prison in 1971 for multiple murders.