Sekulow's comments came shortly after Trump tweeted earlier Sunday that the meeting was simply an effort "to get information on an opponent", which he characterized as "totally legal and done all the time in politics - and it went nowhere".
Until now Mr Trump had claimed that Donald Jr met Natalia Veselnitskaya and other Kremlin lobbyists at Trump Tower in June 2016 to discuss adoptions. Donald Trump Jr. and Jared Kushner expected to get dirt (and would have "loved" to, as Trump Jr. said) but instead the Russians talked about other matters - sanctions and adoptions.
Trump's critics immediately pounced on the new story, the latest of several versions of events about a meeting for which emails were discovered between the president's eldest son and an intermediary from the Russian government offering damaging information about Trump's opponent, Hillary Clinton.
Sekulow's vow comes as another member of the president's legal team - Rudy Giuliani - said negotiations on Trump sitting down with Mueller's team are wrapping.
Last July, Sekulow had said the president "didn't sign off on anything" in regards to the Trump Tower meeting.
Sekulow also dismissed reports the president's son, Donald Trump Jr., is in trouble because of Mueller's probe.
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Trump and his son have both said then-candidate Trump had no advance knowledge of the meeting and that the meeting itself was not useful to the campaign.
The Trump Tower meeting was arranged by British music promoter, Rob Goldstone, who told Donald Jr that he had "information that would incriminate Hillary and her dealings with Russian Federation and would be very useful to your father".
President Trump repeatedly insists there was no collusion between his campaign and the Russian government, and he will undoubtedly continue to maintain that. When it became obvious that the focus of the meeting would not be on Hillary Clinton, Trump Jr. quickly lost interest and the meeting ended soon thereafter.
What Trump acknowledged was that "this was a meeting to get information on an opponent".
"The question is what law, statue or rule or regulation's been violated?" "You then misled the country about the goal of the Trump Tower meeting when it became public".
The federal tax and bank fraud charges Manafort faces are not related to the Trump campaign but Manafort's close relations with Russians and a Kremlin-backed Ukrainian politician are under scrutiny in the trial. "Did I meet with people that were Russian?"
Trump's attacks on the special counsel's investigation have been rebuffed by Republican leaders in Congress who have expressed support for Mueller. If true, it would also mean that Donald Trump Jr. lied about his father's knowledge of this to congressional investigators. In it, lawyers stated that Trump had dictated the statement written aboard Air Force One as it flew back from the G-20 summit in Germany. "They can also cause War!"