Washington and London have told the Syrian opposition that they may stop their support for the group if it refuses to attend the international peace talks on 22 January, an official with the Syrian National Coalition told British media.
The official told BBC and The Guardian newspaper that "The United States and Britain told us we must participate in the Geneva conference".
"They told us plainly that they will stop their support and that we will lose our credibility among the international community if we don't participate," the official added.
The United States denied the news, with spokeswoman of American Department of State Jennifer Psaki saying that John Kerry "didn’t say that the United States intends to stop its support to Syrian opposition".
"Kerry said plainly that the bet is huge for the Coalition, but the international community is satisfied that Coalition's participation is better for it and for Syrian people,", she said.
The Coalition will decide Friday whether to participate or not, although attitudes of its members towards participation are divided.
According to BBC, the official asked whether Washington and London have an "alternative" to Assad.
"They are facing a cruel dictator who uses chemical weapons, and Al-Qaeda. So with whom they will negotiate?", the official asked.
The official said France had not exerted the same pressure on the opposition.
"France asked us to participate, but by saying: We are with you, whatever your decision might be. Saudi Arabia and Turkey were the same," the official added.
Foreign ministers from 11 countries supporting the Coalition includng Britain, Germany, France, Italy, Saudi Arabia, the United Arab Emirates, Qatar, Jordan, the United States and Turkey, renewed their commitments last week to dispel opposition doubts about the talks, particularly related to the departure of Syrian President Bashar Assad. The ministers encouraged the opposition to participate in the conference to be held in Montreux, Switzerland.
Kerry said on Sunday: "I am personally convinced that the Syrian opposition will come to Geneva. It is a test for everybody's credibility. And I rely on both parties' participation".
The head of the Coalition, Ahmad Jarba said in a brief statement during the last meeting of the Friends of Syria that "the most important thing in this meeting is that we agreed that neither Assad nor his family have a role in the future of Syria", also expressing the "fears" and "doubts" on the part of the Syrian opposition.
Translated and edited by The Syrian Observer