William Hague published a picture which showed him standing alongside Hillary Clinton as the US Secretary of State prepares to bow out of her role.
"Warm celebration of US-UK alliance at dinner for Hillary Clinton, and a fond farewell to a Great Secretary of State," he tweeted.
Robert Moore: Hague's farewell tribute to Hillary Clinton
Former president of the United States, and husband of Hilary, Bill Clinton will be among the guests, along with their daughter Chelsea and husband Marc Mezvinsky.
Other guests include: Fashion mogul Oscar de la Renta and wife, General Martin Dempsey, Senator Feinstein, politicians Dr Alan Greenspan and Ms Andrea Mitchell, former White House chief of staff Jack Lew, and his replacement Denis McDonough, French Lawyer Christine Lagarde.
Senator McCain, Acting director of the CIA Mike Morrell, outgoing Secretary of Defence Leon Panetta, American diplomat Dr Susan Rice, and stateman George Shultz.
Senator John Kerry, who has been picked as Hillary's replacement will also attend.
President Obama and Hillary Clinton have spoken of their relationship during a joint interview on CBS's 60 minutes. President Obama heaped praise on the outgoing Secretary of State as she prepares to step down. Clinton would not be drawn on whether she plans to run for presidency in 2016.
Foreign Secretary William Hague will mark the departure of Hillary Clinton as US Secretary of State tonight by hosting a farewell party for her in Washington.
Mr Hague is due to preside over a private farewell dinner for his opposite number during a visit to the US capital where he is expected also to hold meetings with officials, politicians and business leaders.
Yesterday the Foreign Secretary tweeted:
Heading to the US for talks and to host a farewell dinner tomorrow for Secretary of State Hillary Clinton
He also retweeted praise for Mrs Clinton sent to him by Britons:
@williamjhague Please thank her for her continued interest in Northern Ireland. Few are held in such respect here, and use it so positively.
Barack Obama and Hillary Clinton have given a joint interview in which they discuss the past four years, endorsements and health.Read the full story ›
A frustrated Hillary Clinton responded angrily to Republican senator Ron Johnson's questioning about the release of information following the Benghazi attacks.
"What difference does it make?" a clearly exasperated Clinton told the senator, insisting that her focus should be on bringing the militants to justice.
As she began her testimony, her voice cracked at times as she said her work is sometimes highly personal, she told the Senate Foreign Relations Committee:
I stood next to President Obama as the Marines carried those flag-draped caskets off the plane at Andrews. I put my arms around the mothers and fathers, sisters and brothers, sons and daughters.
At another point, she defended UN Ambassador Susan Rice, who was vilified for widely debunked claims five days after the attack that protests precipitated the raid rather than terrorism. She challenged the Republican focus on Rice's comments, which were based on intelligence talking points.
"What difference does it make?" a clearly exasperated Clinton told Sen. Ron Johnson, a Republican, after he pressed her. She insisted that "people were trying in real time to get to the best information," and that her focus was on looking ahead on how to improve security.
US Secretary of State Hillary Clinton has said that Algerian militants involved in the attack on a desert gas plant in Algeria this month had weapons from Libya.
"There is no doubt that the Algerian terrorists had weapons from Libya. There is no doubt that the Malian remnants of AQIM have weapons from Libya," she is speaking at a Senate hearing on the September attack on the US mission in Benghazi, Libya.
AQIM - Al Qaeda in the Islamic Maghreb - is an affiliate of al Qaeda.
Secretary of State Hillary Clinton has said she never saw the requests for additional security for the US mission in Benghazi, Libya, which was attacked in September, because they were handled by other State Department officials and normally would not reach her level.
Clinton is testifying before the Senate Foreign Relations Committee about the September attack by Islamist militants in which the US ambassador and three other Americans were killed.
"The specific security requests pertaining to Benghazi, you know were handled by the security professionals in the department. I didn't see those requests, they didn't come to me, I didn't approve them, I didn't deny them," Clinton said.
She noted that one of the findings of an accountability review board on the Benghazi attack was that "these requests don't ordinarily come to the secretary of state."