French Foreign Minister Dominique de Villepin has asked diplomats to abandon a worldwide strike planned for Monday.
Villepin promised to consider grievances
He admitted that circumstances were "difficult" in a speech to about 600 staff late on Thursday, but said the strike plans were "no ordinary matter".
Union leaders said on Friday they expected 40 embassies and consulates to close in the first strike of its kind.
They are protesting against budget cuts, job losses, reduced overseas allowances and bonuses.
Mr de Villepin's speech, in which he promised to give full consideration to staff grievances, was posted on the internet for the benefit of diplomats overseas.
"Employees do not understand how the president of the republic
and the government can proclaim their grand ambitions for France on
the international scene while at the same time the human and
financial resources available to the ministry are constantly
declining," the unions said in a statement.
The government's budget for next year - which is to be debated in the Senate on Monday - envisages a 2% reduction in foreign ministry costs, and a number of job cuts.
France's foreign ministry network is second in size only to that of the United States employing 9,200 permanent staff and 13,000 local employees around the world..
In addition to 154 embassies there are 98 consulates, and nearly 500 cultural offices and French-language schools.
Their lack of resources was exposed last month when the paper supply company refused to make new deliveries until its account was settled.
Staff had no paper for three days.
"There isn't a kopek at the ministry," said Yvan Sergesse of the UNSA union.
"Half the lifts are out of order because there is no money to mend them. Abroad staff are working up to 14 hours per day."
There have been strikes at the ministry before, but this is the first time that unions have called on diplomats and embassy staff around the world to join in.
"According to the soundings we are getting, it is going well - there is a lot of support," said Daneille Vazeille of the CGT union.