US Secretary of State Anthony Blinken spoke with President Ashraf Ghani on Tuesday night telephonically and expressed his concern over the sharp escalation of violence by the Taliban, the Presidential Palace (ARG) said in a statement.

Both sides discussed the relations between the two countries and the continuation of US cooperation with Afghanistan in various fields, the statement said.

Expressing concern over the escalation of violence by the Taliban, Blinken reaffirmed his country's continued support for Afghanistan's security and defense forces, and stressed the role of the United States in accelerating the Afghan peace process, the statement added.

Both sides also spoke about regional issues and the role of regional countries in the Afghan peace process.

This comes after violence by the Taliban continues to rage in parts of the country especially in Herat, Helmand and Kandahar provinces.

Due to the violence thousands of people are displaced after fleeing their homes while hundreds of civilians have been wounded and dozens killed.

Meanwhile, the United States said on Tuesday that one of many concerns about Afghanistan is that it could spiral into civil war, Reuters reported.

According to the report since the United States announced plans in April to withdraw its troops with no conditions by September 11 after nearly 20 years of conflict, violence has escalated throughout the country as the Taliban seeks more territory.

Peace talks between the Afghan government and Taliban negotiators started last year in the Qatari capital of Doha, but have not made any substantive progress. U.S. State Department spokesman Ned Price said the Taliban saw "the utility of a negotiated solution, they are engaged in Doha."

"If they seek to contravene what they have said, then they will be an international pariah ... and the concern on the part of all of us, one of the many concerns is that the result will be civil war," Price told reporters.

A car bomb blast followed by sporadic gunfire hit Afghanistan's capital Kabul on Tuesday night near the heavily fortified "Green Zone," leaving three civilians and three attackers dead, security officials said.

"It does bear all the hallmarks of the spate of Taliban attacks that we have seen in recent weeks," Price said. "We unequivocally condemn the bombing."