US President Donald Trump tied military aid for Ukraine to Kiev undertaking an investigation that would help Trump politically, a top White House official admitted on Thursday.

Acting White House Chief of Staff Mick Mulvaney’s stunning admission supports a key allegation in the House impeachment effort, that the president illicitly sought foreign political help as he seeks re-election next year.

Mulvaney said it was true that Trump used the aid to prod Kiev in July to investigate the allegation — widely viewed as groundless — that the Democratic National Committee had hidden a computer server in Ukraine that would undermine claims that Trump’s 2016 election victory was helped by Russian meddling.

He further said in a statement that “Let me be clear, there was absolutely no quid pro quo between Ukrainian military aid and any investigation into the 2016 election.

“The president never told me to withhold any money until the Ukrainians did anything related to the server”, Mulvaney added.

Taking to Twitter, Adam Schiff, the House Intelligence Committee chairman who is leading the impeachment enquiry tweeted that, “Mulvaney just said that US military aid for Ukraine was held up pending Ukraine’s investigation of Democrats”.

“Things just went from very, very bad to much, much worse,” he wrote.

Earlier this week, President Trump said that witnesses had provided substantial support for allegations that Trump illegally tried to force Ukraine to investigate his political rival, Joe Biden.

While the White House and Trump’s personal lawyer Rudy Giuliani refused to turn over subpoenaed documents on the Ukraine affair to Congress, House Intelligence Committee Chairman Adam Schiff said five witnesses had backed up allegations of misuse of power that could underpin formal impeachment charges.

Schiff earlier said that witnesses have supplied information showing that Trump’s July 25 phone call with Ukraine leader Volodymyr Zelensky, in which Trump appeared to tie military aid to getting dirt on Biden from Kiev, was planned in advance and then followed up.

Earlier on Thursday, Mulvaney had announced at a raucous briefing that Trump will host the 2020 G-7 summit of world leaders at the Trump National Doral Miami.

The announcement to choose the president’s own club as the site of an international summit comes as Trump is in the midst of twin crises that are consuming his presidency – a hasty and confused American retreat in Syria, and a growing impeachment inquiry in Congress, adding ammunition to Democrats impeachment probe.

On Wednesday, Trump warned his Turkey counterpart Recep Tayyip Erdogan in an extraordinary letter sent the day Turkey launched its incursion into northeastern Syria.

Last week, Turkey launched a cross-border assault on Kurdish fighters after the US decided to withdraw troops from Syria, a move that was criticised by the Republicans, with some terming it a “betrayal” of the Kurds.

(With inputs from AFP)