The US ambassador to Qatar took to Twitter on Tuesday to confirm that her posting will come to an end this month. 

"This month, I end my 3 years as US Ambassador to #Qatar. It has been the greatest honor of my life and I'll miss this great country," Dana Shell Smith said on Twitter on Tuesday.

Many US ambassadors leave their posts after serving about three years.

Yet, there were some suggestions in the US media that Shell Smith was leaving her post because of US President Donald Trump's comments last week that signalled support for Saudi-led moves against Qatar amid a major diplomatic crisis.

But the Department of State said later on Tuesday that the ambassador's decision had been taken earlier this year.

"Ambassador Dana Smith's assignment as Ambassador comes to an end this month and she will depart Qatar later this month as part of the normal rotation of career diplomats throughout the world," a spokesperson said.

"Her decision to leave the Foreign Service was made earlier this year and we wish her the best as she moves on from the Department of State."

Al Jazeera also understands that Shell Smith's decision was taken before the Gulf diplomatic crisis erupted last week.

Gulf Cooperation Council members Saudi Arabia, the UAE and Bahrain, along with Egypt, cut diplomatic, trade and transport ties with Qatar on June 5 claiming that Doha supported "extremist groups".

Qatar strongly rejects the allegations.

Shell Smith's departure comes with Washington sending mixed signals, as senior US officials have been more cautious than Trump and called for dialogue to end the crisis.

Qatar has hired a firm run by former Attorney General John Ashcroft as it works to push back against Trump's claim that it provides support to "terrorist groups".

Hours after the Saudi-led moves were announced against Qatar, Shell Smith had taken to Twitter to repost some of her previous statements praising Doha's efforts in fighting "terrorism" financing and its role in countering the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) armed group.

Criticism by the envoy

Shell Smith was appointed ambassador to Qatar by ex-President Barack Obama in 2014.

Last month, she appeared to express dissatisfaction with political events back home in another message posted on social media.

She took to Twitter in the hours after Trump's dramatic sacking of FBI director James Comey, tweeting: "Increasingly difficult to wake up overseas to news from home, knowing I will spend today explaining our democracy and institutions."

Qatar is home to Al-Udeid, the largest US airbase in the region, which houses around 10,000 troops.

Source: Al Jazeera and news agencies