Dick Cheney, US vice-president, and John McCain, the Republican candidate for the White House, both promised on Monday that Washington’s commitment to Iraq would not waver despite signs of a recent resurgence in violence in the country which has brought the number of US military personnel killed close to 4,000.

The two men’s comments, made on separate trips to Baghdad ahead of the fifth anniversary of the US invasion, contrasted with a setpiece speech on Iraq by Hillary Clinton, the Democratic presidential hopeful, in which she highlighted her vow to start bringing American troops back home within 60 days of taking office.