"I hope the visit will bring about healthy ties in which the Congress will reverse its hostile attitude towards the Sudan, and be a step in the right direction," Ismail told reporters moments before the expected arrival of the US delegation.
Republican lawmaker Smith, who chairs the House International Relations Committee's panel on Africa and human rights, is due to hold talks Thursday with President Omar al-Beshir and First Vice President Salva Kiir.
His visit will come after the death late last month of Kiir's predecessor and southern leader John Garang sparked unrest in the country that threatened a fledgling north-south peace deal sponsored by Washington.
Smith will also visit refugee camps in Sudan's troubled Darfur region to determine whether supplies are reaching the people for whom they are intended and whether attacks on refugees have subsided, his office said.
The US Congress has described the Sudanese government's repression of a rebellion by Darfur rebels over the past two years as genocide.