The US demanded that he went as a precondition to a settlement, but Russian credibility was at stake.
Their demand that Assad step down as a precondition to peace or a political transition has become increasingly unrealistic.
Their release was demanded by Palestinian leaders as a precondition to the peace talks being conducted under the auspices of the US.
Russia is a member of the Middle East Quartet, which demands recognition of the state of Israel as a precondition to a seat at the negotiating table.
Instead, Obama berated Abbas for insisting on a freeze on new settlements as a precondition to re-starting peace talks, calling them merely "an irritant".
"We've actually done almost everything that Republicans asked to be done several years ago as a precondition to move forward on comprehensive immigration reform".
North Korea complains it still has not received roughly $25m frozen in accounts in a bank in Macau it regards as a precondition to closing the reactor.
The Palestinians have demanded an end to all Israeli settlement building, including in East Jerusalem, which they claim as their future capital, as a precondition to direct talks.
In a clear shift in American policy, they showed the Obama administration was no longer insisting on an end to hostilities as a precondition to talks.
The former ruling party's intransigence it insists, for example, on Mr Gbagbo's release as a precondition to political participation could leave it marginalised.
Israel has freed a number of Palestinian prisoners while the Palestinians have dropped their demand for Israel to stop settlement construction as a precondition to talks.
