U.S. Secretary of State John Kerry flew to Brussels and London on Monday, June 27 to urge British and European leaders not to allow anger to poison their divorce proceedings, AFP reports.

Washington was dismayed by last week's "Brexit" referendum vote to quit the European Union, which sent shockwaves through world markets, but insists its ties with Britain and the EU remain strong.

Scrambling to adjust to the now uncertain Western geopolitical map, US officials say they have no solution themselves to the political crisis in London and Brussels.

But Kerry, as he met Britain's outgoing prime minister David Cameron and EU Commission chief Jean-Claude Juncker, urged both parties to negotiate the split amicably.

"It is absolutely essential that nobody loses their head, nobody goes off half-cocked, people don't start ginning up scatterbrain or revengeful premises," he said in Brussels, according to AFP.

Some European leaders have suggested that the Union take a tough stance on Britain as it negotiates an exit from the 28-member bloc to dissuade others from following suit.

But Kerry reminded officials in both Brussels and London that the Western allies still have too much at stake in terms of economic and political stability to risk division.

"Yes, the EU and UK relationship will now change," Kerry told reporters at the British Foreign Office in London after talks with Foreign Secretary Philip Hammond.

"But what will never change is that we are strongest when we stay together as a trans-Atlantic community and find the common ground rooted in the interests and values of freedom, open markets equality and tolerance."

Kerry said that Washington hopes that both Britain and the European Union remain strong after Brexit, but did not hide U.S. disappointment at British voters' decision.