The United States is "gravely concerned" about opposition leader Raila Odinga's swearing-in as the people's president.
The NASA chief insists president Uhuru Kenyatta is an illegitimate ruler and that Kenya urgently needs saving.
He took what has been termed a symbolic oath at Uhuru Park in Nairobi on January 30.
More on this: Raila 'sworn-in' as people's president, Kalonzo absent
In a statement on Thursday, the US noted: "We reject actions that undermine Kenya’s constitution and the rule of law. Uhuru Kenyatta was elected as president of the Republic of Kenya on October 26, 2017 in a poll that was upheld by Kenya’s Supreme Court."
The country led by Donald Trump further noted that complaints regarding this determination should be addressed through appropriate legal mechanisms.
The US also addressed police behaviour on the day of Raila's 'inauguration'. Kenyans had been worried about injuries and deaths as police had pledged to do whatever it took to maintain law and order.
They had reported to the park but were later withdrawn, a curious move in a country whose opposition gatherings are known to be chaotic.
Raila claimed 215 of his supporters were killed by police during the elections period last year. The first vote took place on August 8, 2018 and Uhuru and deputy president William Ruto were finally sworn-in on November 28.
"We commend the restraint shown by security forces and urge them to continue to refrain from any unnecessary or excessive use of force," stated the statement by Department of State spokesperson Heather Nauert.
"Any arrests and prosecutions must be made in full accordance with the rule of law and demonstrate transparent due process."
The United States asked the public to shun violence and hatred, and noted that demonstrators have the right to gather and express their views freely.
Trump's country further addressed the media shutdown by the government, which it noted was restrictive and intimidating.
"Freedom of expression, including for members of the media, is essential to democracy and is enshrined in Kenya’s constitution. We urge the government and all Kenyans to respect freedom of expression and implement court orders calling for the restoration of television broadcasts."
A national conversation was recommended for the sake of cohesion and addressing issues that have lasted long.
"The United States continues to support efforts by religious, business, and civil society leaders to begin this conversation in the near future and calls on everyone to participate in this endeavor."
The superpower promised to stand firmly with Kenyans as only they can find solutions to their problems and make plans for this "great country".
Raila explained himself on Thursday, saying he was not mad to lift a Bible and take the oath.
He claims he got 8.1 million votes in the original election and that his arch-rival managed 7.9 million.
"I can swear by the Bible that the results we released last week were genuine. We won the elections while Jubilee lost. That is why I was able to hold the Bible. I did not hold it because I am mad or a megalomaniac," he said at Okoa Kenya in Nairobi.
Raila, Kalonzo Musyoka (Wiper), Musalia Mudavadi (ANC) and Bungoma senator Moses Wetang'ula (Ford Kenya) revealed on Thursday that NASA's delayed oath-taking was strategic and reiterated that they remain united.
Details on this: I wasn't mad to swear by Bible, delayed oath a strategy - Raila
Also read: How Wanjigi pushed Raila to be sworn-in