Huma Abedin, a longtime close aide to Hillary Clinton, has written in a new book that she was sexually assaulted by a US senator, an incident she “buried” until allegations against the supreme court justice Brett Kavanaugh triggered her memory years later.

Abedin makes the shocking claim in a memoir, Both/And: A Life in Many Worlds, which will be published next week. The Guardian obtained a copy. Abedin does not name the senator or his party or give any other clues as to his identity.

Abedin details her alleged assault while describing her work for Clinton when the former first lady and future secretary of state and presidential candidate was a US senator from New York, between 2001 and 2009.

The passage comes shortly after a description of how Abedin and the Clintons came to attend Donald Trump’s wedding to his third wife, Melania Knauss, in Palm Beach, Florida, in January 2005.

Of that occasion, Abedin, who was born in Michigan but grew up in Saudi Arabia, writes: “I felt I was at an Arab wedding back home.”

Then, after describing a Washington dinner attended by “a few senators and their aides” but not Clinton, Abedin writes: “I ended up walking out with one of the senators, and soon we stopped in front of his building and he invited me in for coffee. Once inside, he told me to make myself comfortable on the couch.”

She says the senator took off his blazer, rolled up his sleeves and made coffee while they continued to talk.

“Then, in an instant, it all changed. He plopped down to my right, put his left arm around my shoulder, and kissed me, pushing his tongue into my mouth, pressing me back on the sofa.

“I was so utterly shocked, I pushed him away. All I wanted was for the last 10 seconds to be erased.”

Abedin writes that the senator seemed surprised but apologized and said he had “misread” her “all this time”. As she considered how to leave “without this ending badly”, she writes, the senator asked if she wanted to stay.

“Then I said something only the twentysomething version of me would have come up with – ‘I am so sorry’ – and walked out, trying to appear as nonchalant as possible.”

Abedin writes that she kept away from the senator “for a few days” but then ran into him on Capitol Hill, nodding when he asked if they were still friends. Clinton then joined them, Abedin writes, “as if she knew I needed rescuing even though I’d told her nothing about that night”.

Abedin writes that she stayed friendly with the senator and soon “buried the incident”, which she wanted to forget, succeeding in erasing it from her mind “entirely”.

Then, in late 2018, Kavanaugh was nominated to the supreme court by Donald Trump. A professor, Christine Blasey Ford, accused Kavanaugh of sexual assault at a party years earlier, an allegation Kavanaugh denied.

Testifying in the Senate, Ford said the alleged assault “drastically altered” her life, before a therapy session in 2012 led her to do her “best to suppress memories of the assault because recounting the details caused me to relive the experience, and caused panic attacks and anxiety”.

Though Kavanaugh became a leading symbol of the #MeToo era, in which allegations of sexual misconduct and assault have brought down prominent men, Republicans did not waver in their support of his appointment and he was duly confirmed to the court.

Abedin’s memory of her experience on the unnamed senator’s couch, she writes, was triggered when she read about Christine Blasey Ford “being accused of ‘conveniently’ remembering” her alleged assault.

Earlier this month, an excerpt from the book published by Vogue dealt with Abedin’s experiences when her husband, the former congressman and New York mayoral candidate Anthony Weiner, became embroiled in repeated scandal over sexually explicit behavior on social media.

Abedin and Weiner are now estranged.

Information and support for anyone affected by rape or sexual abuse issues is available from the following organisations. In the US, Rainn offers support on 800-656-4673. In the UK, Rape Crisis offers support on 0808 802 9999. In Australia, support is available at 1800Respect (1800 737 732). Other international helplines can be found at ibiblio.org/rcip/internl.html