"If he doesn't get a good increase, it is likely that the next secretary general will come from elsewhere. Other countries are increasing their defense spending in a serious way," a source told the British daily.
Countries like France, Germany and Poland have already announced significant hikes in military spending, whereas the United Kingdom is expected to up its defense expenditure by just enough to keep pace with inflation.
A NATO source told the daily that France would prefer the next NATO secretary general to come from an EU country, such as Poland.
The names of Estonian and Lithuanian prime ministers have also been mentioned, although some allies reportedly fear that giving the top NATO job to a Polish or Baltic leader could generate too much hostility with Russia.