The October deadline for Britain and the European Union to enter a new phase of Brexit talks is looking "very challenging", the Government has warned.
Taoiseach Leo Varadkar said that it was not yet possible to say whether the European Council would be able to agree that sufficient progress had been made on a number of key issues to allow negotiations to move on to phase two.
Speaking at an All-Island Civic Dialogue on Brexit in Dublin on Thursday, Mr Varadkar said while Prime Minister Theresa May's speech in Florence last week was welcome, "it does not yet bring us to where we need to be".
"The timetable for the negotiations envisages the leaders of the 27 remaining member states - including Ireland - deciding next month whether sufficient progress has been made on the three key phase one issues - citizens' rights, the financial statement and issues relating to Ireland.
"Right now, that timetable looks very challenging.
"While we have seen some progress, significant gaps remain and time is fast running out."
The Taoiseach again insisted that there could be no reintroduction of a border on the island.
He also warned that anxiety about the border issue "extends far beyond the impact on trade and balance sheets".
"It is also about the emotional impact on communities, North and South, which have become increasingly intertwined over the past two decades," said Mr Varadkar.
"There is, understandably, heightened concern among communities who are worried about how their rights will be protected, including rights arising from citizens in Northern Ireland retaining EU citizenship after Brexit.
"And, above all, there is concern that reintroduction of a border will be a step backwards, a step in the wrong direction in terms of the security, peace and political stability."
Mr Varadkar vowed that as co-guarantor of the Good Friday Agreement, the Government will continue to do all it can "to protect and support the hard-won peace on this island".
The Taoiseach said many people were already feeling a "Brexit effect", due to currency fluctuations having an adverse impact on businesses.
"General uncertainty surrounding the future relationship with the UK is also delaying investment decisions and long-term planning," he said.
"We are not complacent about these challenges. We have already taken action and there are a number of other measures in train to support businesses in the face of economic risks from Brexit."
Referring to the Northern Ireland political situation, he said it was almost nine months since the collapse of the institutions.
"The need to achieve a solution to the political impasse in Northern Ireland has never been more imperative," he said.
Foreign Affairs Minister Simon Coveney said a post-Brexit transition period could last up to four years.
"When we get to the point of negotiating and debating a transition arrangement ... I think we will be talking about a period of somewhere between two and four years.
"Britain is very anxious to move forward to talk about phase two issues. The European Union side has really been sticking to the rules we set at the start - we must make progress on the phase one issues first," he said.
Mr Coveney said these issues are citizens' rights, financial settlements and Irish border issues, a Common Travel Area and protection of the Good Friday Agreement.
The minister said significant progress has been made on clarity around a financial settlement, citizens' rights and the Common Travel Area.
However, he added that more progress is needed around bringing clarity to the border issue.
Mr Coveney also said Brexit would be made much easier if the UK remained in a customs union and had a close partnership with the single market which allowed free trade to continue.
"But that is not compatible with some of what Britain has been saying in terms of their ambitions to negotiate free trade agreements across the world," he added.