Foreign ministers from the Group of Eight most industrialised nations are due to meet in Germany on Wednesday before next week's G8 summit.
Mr Gabriel (R) says time is running out for a deal on climate change
They will hold talks on a range of issues including climate change, Iraq, Iran's controversial nuclear programme, Darfur, Kosovo and Afghanistan.
The Middle East Quartet will also hold crisis talks on violence in the region.
Germany's environment minister has told the BBC it would be hard to reach a deal with the US on climate change.
As foreign ministers arrived in Potsdam for the pre-summit talks, German Environment Minister Sigmar Gabriel told BBC News time was running out on a possible agreement over measures to combat climate change.
"We know that with the Americans - and not only the Americans, but also the Chinese and some others - it will be very difficult to come to a real treaty during G8, maybe we cannot come to an agreement," Mr Gabriel said.
"Then the public pressure on those heads of state who rejected the step forward on climate policy will be much higher than today."
Germany has made climate change a top priority for its 12-month G8 presidency. Chancellor Angela Merkel is pushing a deal to limit the rise in global temperature to 2C (3.6F) this century and reduce greenhouse gas emissions to 50% below 1990 levels by 2050.
It has also invited the foreign ministers of Afghanistan and Pakistan to the Potsdam talks, hoping to improve strained relations and economic ties between the two countries.
The US, meanwhile, will push for new sanctions against Iran over its uranium enrichment programme, Secretary of State Condoleezza Rice said.
"We are firm about the need to continue to increase the pressure and we are firm that, should Iran make a different choice, we are prepared to go that way as well," Dr Rice said.
Iran insists its nuclear work is for peaceful purposes.
Dr Rice will also discuss plans for Kosovo's transition to independence and push for a new UN Security Council resolution on Sudan's war-torn Darfur region.
Members of the Middle East Quartet - the US, the UN, the EU and Russia - will also hold crisis talks amid spiralling violence in Lebanon, Israel and Gaza.
The talks were intended "to accompany the efforts of the players on the ground," German officials said.
G8 leaders will meet at in the German Baltic Sea resort of Heiligendamm from 6-8 June.