US Secretary of State John Kerry has expressed caution over whether peace talks on Afghanistan with the Taliban can take place.
A row over the status of a Taliban office in Qatar’s capital Doha has overshadowed efforts to start peace negotiations there.
Mr Kerry said he did not know if the talks could be put back on track.
However, the US special representative on Afghanistan, James Dobbin, is reported to be in Doha.
A US official was quoted by the AFP news agency as saying that Mr Dobbin, who is responsible for both Afghanistan and Pakistan, would have talks with Mr Kerry and Qatari officials.
Mr Kerry told reporters in Doha: “We need to see if we can get back on track.”
However, he added that he did not know if that was possible or not.
“We are waiting to find out whether the Taliban will respond,” Mr Kerry said.
Mr Kerry said that if the Taliban did not decide to “move forward” in the near future, the Taliban office in Doha might have to be closed.
Washington had announced on 18 June that it was opening direct peace talks with the Taliban in Qatar, as Nato-led combat forces prepare to leave Afghanistan by the end of 2014.
The US met the Taliban secretly in 2011 in Qatar, but these would be the first open talks.
Afghan President Hamid Karzai announced his government was also sending negotiators to Qatar to meet the Taliban.
But a row broke out over the status of the Taliban office, which the Afghan government sees as an attempt to confer legitimacy on the insurgents.
The Afghan government objected in particular to a nameplate, which included the worlds “Islamic Emirate of Afghanistan”, and a white-and-black flag.
After complaints from the Qataris, the Taliban removed a nameplate and a flag, only to hoist the white-and-black banner again on a shorter flagpole.
Kabul said the peace talks issue had been badly handled and the Afghan foreign ministry accused the Americans of acting in bad faith.
“The manner in which the office was established was in clear breach of the principles and terms of references agreed with us by the US government,” the ministry said in a statement.
American assurances that the flag and nameplate would be completely removed have failed to assuage Afghan anger.
Mr Karzai has insisted that the peace process must be Afghan-led without interference from “foreign powers”.
He also suspended security talks with the US on the American presence in Afghanistan.
The Taliban office opened on 18 June – the same day that Nato handed over security for the whole of Afghanistan to the Afghan government for the first time since the Taliban were ousted in 2001.